After all, lore wise I see no reason one wouldn't be able to enter the simulation again, so long as they kept the suit... It's a computer program, you can go about hacking every terminal in the Capital Wasteland (/mojave), why can't you reboot a simulation? Or even if you didn't make the missions playable, at least enter it?
Just a side query, considering learning the GECK, although not sure if I just want to move over to the fourth game, so right now it's just something I'm contemplating.