what happens to trades that aren't accepted?

[Grumble_tash]

I tried to trade some gc for some horses, the gold disappeared from my store but the trade was neither accepted nor declined. Will this state of limbo exist in perpetuity? or can i cancel the trade offer?

[Konshens]

If a trade request is neither accepted nor cancelled within 8 hours, your resources will then be returned.

[Ferro219]

In addition to Konshens' answer:
If resources are returned and you do not collect them for some time, they will be removed from your mailbox as well.