I was really bored and got 18k points for the Gimme a patch! wish, but I can't find the patch. Does anyone know where it is supposed to be?

I'm guessing it appears somewhere within or nearby the livid farm as soon as you claim the wish.

 

Edit: seems that once purchased the allotment plot appears and once you harvest what ever you plant it disappears again.

My friend had the same problem he showed it too me screensharing and on lowest graphics settings you can't really see the patch. You might need to turn on ground detail or something like that, but I think its to the east of the livid farm and it does dissapear after one use.