You can search your history (CTRL+H or the corresponding menu entry) for them, or you can use the address bar to find them: simply enter part of their name or address (it doesn't need to be the start, you can enter parts in the middle) into the address bar, and it will display a list of matches for that part.

If you can't find them that way, it's possible that they were deleted from your history, for whatever reason ("Clear recent history", an accidental "Delete" tap when hovering them or whatever). I recommend you bookmark links you want to remember later, since that is the easiest and safest way to keep track of them.