I tapped Coal, Stone, Corn.. also making note of my inventory amounts and also Runes.
When trade expired.. I rechecked all. Nothing had been taken nor given... 100% sure.
If your fish had been taken.. this may mean u used one during the expiring time lapse or this works different for different kingdoms.
I loose from my inventory only when I do partial trades.. thus confirming with big delivery tab, but not when I allow trade to expire, without tapping big delivery tab.
edit: next trade I will check inventory amounts before 'checking' item.
trade above I took note of amounts after 'checking item'.
will add results to post.