eBay removed all traces of the old Collections feature well over two years ago, as far as I can tell. Perhaps you are actually referring to something else you used to keep track of items of interest?
More recently, eBay removed the old "All Lists" page, which provided a convenient link to items on the Watch List and other custom lists in one place.
Your custom lists should still be reachable using a desktop browser to go to your Watch List page, and clicking on the large "Watchlist" heading to reveal a drop-down menu of your custom lists.
If that is not what you are referring to, could you explain how you reached the items you were keeping track of?
