Without having seen your script, I can only surmise that if the first table is re-sorting or re-finding when the user goes back to it, then there must be a step in the script which is doing the re-sorting/re-finding, in which case removing that step would appear to be the simplest solution.
I could be way off base though, so perhaps post your script so we can see...
Leaving a layout with a specific found set and specific sort order and then returning to it should NOT change your record set when all you are doing is changing layouts. Finds and sorts as user-specific so as sunmoonstar_13 suggested, something appears to be happening. Are you using Go To Related by chance?
Anyway, one lazy easy way is to start your script with two steps:
... you can then go to your other layout and do your thing (in the new window) then close the window and you will be right back where you started (and on same found set and sort order). You can also preserve found sets by performing a table occurrence switchero using Go To Related but you need an additional table occurrence (which doesn't even need to be related).
With something simple as you've described, I'd just open a new window but it begs the question ... why is your record set changing when you return using only straight layout switching?