Go to market hit menu then downloads and see if its there for you. If not go to market and download it back to your phone.
What cyrock is saying is that when he/she went to the market to search and re-download it, it's not there. My friend had the same issue yesterday. It looks like the Mabilo app developers took it off the market. What I don't get, though, is that for us who still have it...it works fine. I wonder if it will ever be put back up for download? Cyrock, what my friend did was used an app plainly called "ringtones" (it was one of the first apps that came up in the search results) and she said it's pretty much just as good as Mabilo Ringtones.