Started my computer for the first time in a few days. Ran some updates. MSFS gone. Needed to reinstall.
I also lost all my settings and had to reinstall when joining the beta-program.
This is not good enough.
Compare to X-planes flawless beta changeover as an example.
Please, don’t do another public beta run, before this system has been improved.
Please don’t join another public beta run if you’re not prepared to do a reinstall, or if you don’t know how to back up your game content to avoid a reinstall.
It’s well documented that reinstall is likely / necessary. The sign up is full of disclaimers.
This one’s on you.
You know all that stuff you are supposed to read when you join a beta? This was at the top, and your issue could have been avoided.
X-Plane is a different, and in this case simpler beast.
I suspect since MSFS runs on servers, the beta has to live on a different server entirely, so everyone in the released version doesn’t have to deal with beta issues and vice versa. This leads to update issues when the path to update final releases is through the vanilla version, not the beta, and a user fails to READ THE INSTRUCTIONS.
What the vanilla server sees is basically a corrupted game, so it replaces the whole thing. Because the beta version never lives on the vanilla servers. It is up to you to switch things back after beta, or just expect the annoyance of downloading the files again every two months.
Or skip the beta. Which really, is probably the best approach if technical issues like this bother you. Because a beta ALWAYS can have some game breaking tech issues.
Anyway, we have all been there at one time or another. Some of us have been there with MSFS beta! More than once! 
Sorry mate, this one is on you…
RTFM.
The instructions for the beta were very clear, including the warning that it may wipe out your install after the beta. If you jumped in without reading the instructions, this is on you.
That said, it’s a very clunky beta process that really needs to be simplified.
I’ll go and get the burn cream ready for OP
As @MortThe2nd pointed out, before joining a beta, please read the notices that are posted.
