Board Thread:Questions and Answers/@comment-24180266-20140118164742/@comment-24145588-20140118180454

Your question isn't very clear, Milo27, but see if this helps.

One monster per island will be in the "buyback" slot of the market. So if you've recently sold off (for example) a Spunge on the Cold Island, a Tweedle on the Air Island, and a Reedling on the Water Island, you would be able to buy those back, for the same price that you sold them for.

If you sell another monster on the same island, it replaces the previous one in the buyback slot. Once it's gone from there, there is no way to get it back.

If you want to remove a monster from your island to make room for others, but you think you might want it back later, the Hotel Structure is a good option. You can store monsters in there without losing them. They don't sing, and don't earn money, but you don't lose them. Also, if you have a Unity Tree on your island (which you always should), monsters in the Hotel still contribute toward making other active monsters happy.