I don't think it's ever happened at our gym, once a girl leaves team she doesn't usually try and come back. I'm sure exceptions would be made, depending on why the decision was made to leave team in the first place.
I cannot think of a single girl who has done that in the 7yrs we have been at our gym... honestly going back to rec has happened a few times but only with girls in L3. Anything beyond that and they either decide to do Xcel, try cheer (we have a second gym with a nice cheer program) or quit altogether.
I did this! I was chosen for the fast-track pre-team program when I was in kindergarten (probably age 5, we were working on slowly developing old L4 skills). I decided I actually just wanted to play with my friends so I asked my mom if I could quit. I came back and did some rec stuff for a while when I was like 7 or 8, but I wasn't ready to work hard and focus. I went on to other activities and came back to gymnastics when I was 12, this time knowing that gymnastics was what I wanted to do. I made team when I was 13 and competed for 5 years, making it up to old L7.
It's definitely possible, especially if things change for the gymnast between the decision to quit team and the decision to come back. But it's not that common. More common is kids who quit gymnastics and come back several years later knowing that this is what they want and they're ready to commit to it. Especially because after a few years of team, rec classes probably wouldn't be at the right level for a team gymnast, so it would make more sense for them to want to switch sports or do something like T&T. When they're at that point of having recently joined team and they want to go back to rec, it might just be that team wasn't what they thought it would be.
I have only seen this happen at the pre-team level for young kids. They were invited and tried pre-team at age 4-6, but decided that structure wasn't fun enough or they weren't ready to focus, so went back to rec for a while before trying the team track again after they matured a little more. Those stories seem reasonably common (though I'd say many, if not most littles, do not actually return to JO team track after trying it once and not liking it).
As mentioned by another poster, I would think after about L3, there aren't a lot of Rec programs with high enough skills for a team kid to switch into and be challenged at all. Perhaps Xcel Bronze to Rec and back could be a possible path if for some reason a girl wasn't ready for, or couldn't commit to, the competition demands that year. Xcel is typically pretty welcoming, so coming back to Xcel after a break (for any reason) is, I think, generally acceptable and possible. Returning to JO is generally very, very difficult.