I have been tossing back into the rift for a few days and it just gets me the rift pie back. It was amusing the first 2 times then the next few concerned me. Not sure its supposed to happen multiple times.

It happens because the item has "pie" in its name, which is the keyword for getting that item from the rift. Most items you toss in will give you a random item, but some special items have certain keywords where you will always get the item associated with that keyword, or you'll get nothing since all items have a random chance of not giving you anything.

I don't think this is a bug, it's just how the rift is programmed.

I've tossed it in before and have gotten it taken or a different item.

How long ago was that? Because I think there were still some issues with the keywords back in the beginning that got fixed, so it may be that.