Hi..I actually have a Samsung android tablet
Was this under Google Play or Samsung's app store?
If under Samsung: Doesn't Samsung provide a option in your account to look at what you have/purchased? It should be there but I don't know for sure what stipulation Samsung had since I think PS Touch was a freebie for Samsung users.
If under Google Play: Sign into Google Play with your Google account that you bought PS Touch with > Apps (in the upper left) > My Apps. PS Touch should be there.