The mystery of the missing USD

[theoretical]

Just to see what would happen, I sent 15 USD to cover a short with only 10 USD of value.  The extra 5 USD seems to have disappeared!  What happened to it?  (Log attached, I edited it to only show relevant parts.)

EDIT:  This is on dry run 12 testnet.

I always thought:

- A short would be implemented by allowing an address to carry a negative USD balance, in which case (some portion of) the positive XTS balance representing the collateral would be locked to that address.
- Covering a short can be done by sending USD to the short address, if the wallet controls another address that has a positive USD balance.
- Covering a short can also be done by issuing a market order to buy USD for XTS, the order is allowed to use XTS from the collateral in proportion to the negative balance that would be erased.

I have some USD from a successful ask order, so I thought the wallet_market_cover command would simply send USD from one address's positive balance to erase another address's negative balance.  This is apparently not what happened, since my balance declined by 15 USD.

The USD disappearing makes no sense!

Code: [Select]

default (unlocked) >>> wallet_market_order_list USD XTS
TYPE        QUANTITY            PRICE                         BALANCE             COST                COLLATERAL          ID
================================================================================================================================
short_order 11,271.64557 XTS    0.0079 USD / XTS              11,271.64557 XTS    89.0460 USD         N/A                 XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
cover_order 224.55088 XTS       0.00445288836098081 USD / XTS 0.9999 USD          0.9998 USD          299.40118 XTS       XTSFnFEATWvtgcpVoncesBWygRJ317EkgPEH
cover_order 22,455.08982 XTS    0.00445332888007125 USD / XTS 99.9999 USD         99.9998 USD         29,940.11976 XTS    XTSArZdx8nJayA8z4WrCQjE21mf5v5r7Y5ng
cover_order 189.87340 XTS       0.00526614049150644 USD / XTS 0.9999 USD          0.9998 USD          253.16454 XTS       XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
cover_order 1,890.00000 XTS     0.00526666666666666 USD / XTS 9.9540 USD          9.9539 USD          2,520.00000 XTS     XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
default (locked) >>> wallet_market_cover drltc 1 USD XTSFnFEATWvtgcpVoncesBWygRJ317EkgPEH
default (unlocked) >>> wallet_market_order_list USD XTS
TYPE        QUANTITY            PRICE                         BALANCE             COST                COLLATERAL          ID
================================================================================================================================
short_order 11,271.64557 XTS    0.0079 USD / XTS              11,271.64557 XTS    89.0460 USD         N/A                 XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
cover_order 22,455.08982 XTS    0.00445332888007125 USD / XTS 99.9999 USD         99.9998 USD         29,940.11976 XTS    XTSArZdx8nJayA8z4WrCQjE21mf5v5r7Y5ng
cover_order 189.87340 XTS       0.00526614049150644 USD / XTS 0.9999 USD          0.9998 USD          253.16454 XTS       XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
cover_order 1,890.00000 XTS     0.00526666666666666 USD / XTS 9.9540 USD          9.9539 USD          2,520.00000 XTS     XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
default (unlocked) >>> wallet_market_cover drltc 15 USD XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
default (unlocked) >>> wallet_account_transaction_history drltc USD 2 17000
 RECEIVED            BLOCK     FROM                TO                  AMOUNT                  MEMO                                        BALANCE                 FEE                 ID
================================================================================================================================================================================================
|2014-08-10T23:48:32 17286     drltc               COVER-FnFEATWv      1.0000 USD              payoff COVER-FnFEATWv                       0.0000 USD              0.00000 XTS         ae2f47b1|
|                              COVER-FnFEATWv      drltc               299.30118 XTS           cover proceeds                              299.30118 XTS                                       |
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|2014-08-10T23:55:36 17327     drltc               COVER-2886bmzN      15.0000 USD             payoff COVER-2886bmzN                       0.0000 USD              0.00000 XTS         bb116fb6|
|                              COVER-2886bmzN      drltc               2,519.90000 XTS         cover proceeds                              2,819.20118 XTS                                     |
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
default (unlocked) >>> wallet_market_order_list USD XTS
TYPE        QUANTITY            PRICE                         BALANCE             COST                COLLATERAL          ID
================================================================================================================================
short_order 11,271.64557 XTS    0.0079 USD / XTS              11,271.64557 XTS    89.0460 USD         N/A                 XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF
cover_order 22,455.08982 XTS    0.00445332888007125 USD / XTS 99.9999 USD         99.9998 USD         29,940.11976 XTS    XTSArZdx8nJayA8z4WrCQjE21mf5v5r7Y5ng
cover_order 189.87340 XTS       0.00526614049150644 USD / XTS 0.9999 USD          0.9998 USD          253.16454 XTS       XTS2886bmzNNa4ajh3o6eVvVYo9mc2Ca2RZF