There are a few things that detect collisions in patching for those systems that don't do relocation.
However that is seldom the whole story.
Sometimes you get patches that overwrite the same area deliberately (someone might make a translation and another tweak some wording, change the font,
Sometimes the data location changes within a game; the ever popular "just move it to the end" method used in quite a few games (especially ones without banks or similar fun, though they are hardly immune either -- for the GBA and files within DS ROMS and PSP stuff it is almost the default method) means I can doodle all over a sprite but if the pointers say the sprite is at the end of the game/file now it is not going to change a thing. Indeed this might be the method you use to fix a collision that matters.
Beyond that sometimes there are overwrites within the same area that, albeit unintentional, do not trouble anything.
Ignoring all that though then even if there was not a file your hex editor if you have one of the big boy ones (say hex workshop) should be able to do a file compare and tell you what has been changed. Copy and paste/export the results of both compares and you can view that data, make a spreadsheet or do what you need to do. If you got really bored then most IPS patches are a list of location and change data.