Imagine you want to find a subset of your records and then go to a particular one, by script. If it wasn't a subset you could do a script find for the record you want. Now you have a subset of one. Then you could do a step to Show All but it will stay on the record you were on. You can't do that with a subset. You can't find Joe Blow, then do a Find for all the people with red hair but still land on Joe Blow when you're done (assuming Joe has red hair). So here's a way to do it.
Make a field with global storage, of the same type as your unique key field. Make a calculated field that says if key = global then it equals 1 else 2. Find Joe Blow. Set Field global to equal key. Joe now has the only calculated field that = 1. Do your find of red hairs. Sort by calculated field. Joe will be on top. Go to the first record, that's Joe. Now sort by your normal order (last name or whatever) but the sort doesn't disturb what record you're on so you're still on Joe.