Right now the only way to regenerate resources is to restart the game, which is kinda lame, but I'm planning to change that in a future update.
The game also doesn't remember any half-purchased items, but you can hold right mouse button to take back any items you put in the crates, restart the game, and collect more items if you're missing any.
In a future you'll also be able to cancel trades, right now it's not possible, sorry!
I also just released a quick little fix that made mushrooms twice as common since they were a bit too rare.
Thanks for the feedback!