The short answer is - it depends, which isn't much of an answer
So, I found Glorious Glos cache years ago but now through adoption, I own it - I can't see any issue with this.
I would have thought before you adopted a cache, you would have had some interest in that cache, so therefore had already found it. But, if for some reason you hadn't found it and adopted it, then no.
Caches you've put up for adoption - There are different levels here:
1) Is any special knowledge needed to find this cache e.g. solving clues or cyphers, travelling distance to collect information you already have, etc
2) Ingenious cache hides (similar to 1 above but this is about the physical side)
3) Regular caches
Case 3: I can't see any issue once adopted, they aren't your caches, so yes especially as we all know, caches get moved about at GZ and sometimes you can't find your own caches doing maintenance
Case 2: This is more difficult especially if the D/T is an unusual one, as you know what to look for
Case 1: If you go through the steps a cacher with no prior knowledge would go through, yes but also case 2 applies here.
Helping a CO place a new cache - There are different levels here:
1) Did you physically place the cache in the 'hole' for the CO
2) You visited the site but the CO placed it while you weren't looking or not there
3) You just helped with the listing and suggested hiding spots but hadn't visited GZ
I think in any of these cases, yes you should be able to find this cache but for cases 1 & perhaps 2: no FTF, case 3: I would let others have chance for a FTF as you had prior knowledge but are you that desperate for a FTF
As TJ says:
Ultimately, it is only yourself you have to satisfy