The tone of this thread suggests that you're in a "no win" situation. In fact, I look at it differently -- you're in a "no lose" situation.
Your options:
1. You can walk away from the fellowship, and practice gen surgery. It will be a match violation but who cares? You will never be in the match again.
2. You can start the fellowship. Maybe it will be fine. Maybe it will suck. Who knows? Sounds like it was better a short while ago. Maybe they will turn it around in the next year. Show up and see how it goes. What's the worst that can happen? If it's horrible, you can just quit. Get a GS job. You're in the same place as option 1, except perhaps with an employment gap (unless you keep your fellowship job while looking for a GS position). You might even be able to moonlight in any gap.
3. You could review the institution's website and see if the exit of the faculty is mentioned (or, see if they are no longer listed). If not, google them and see if they show up somewhere else. Then you could innocently email the PD and mention that you're excited to start but by looking at the institution's website and using google you noticed that many of the faculty you met have left. See what happens.
4. You could start the fellowship and discover there are not enough cases for full time training. Maybe they would be willing to hire you 1/2 time to be a general surgeon, and 1/2 to be a fellow. Might take twice as long to train, but you'd have 1/2 the salary of a gen surgeon.
5. You could start the fellowship and get orphaned by the program closing. In that case, your funding might be able to transition to a new program, and they may be able to get a temporary complement increase to take you. You might end up somewhere better. Worst case, you're back to GS.
The only thing you can't do is look for a new fellowship, assuming this one was in the NRMP match. You'd need a waiver first if you wanted to do that.
From my vantage point, it depends how much you want this field. If you really want it, I see not much downside to starting the fellowship. if it works out, then all is well. If not, you just end up back in GS which is your default option.