The muscle mass you lost/will lose , I am sure you will recover it no problem and be back to where you were before, muscle memory. DO NOT freak out about losing muscle & start overdoing it then possibly getting hurt or affecting your new friends.
Through personal experience if the scale was dropping & I wasn't training, I definitely think muscle loss is inevitable. I think I took 3 weeks then 2 weeks then 4 weeks off total and I looked flat & depleted. Whether I was eating a caloric deficit or excess while NOT training, I lost muscle either way. The only way I think you can be certain is if you got your bf done before & compare that to now and look at the LBM, even THEN I think there is a margin for error. If you are eating maintenance, NOT below, that is one of the best ways to well, 'maintain' ... but there still may be some loss, just prevents too much if you know what I mean.
I think it is important that you nourish your body while the insides are trying to recover though, and not limit veggies (all the colors), fruit & other nutrionally plentiful foods. This MAY not be in line with your current diet.
If I were you I would focus on what you're doing, getting back in there, baby steps, working yourself up to 'more' weight ... you'll get back to where you were, your mind is in the right place and that is all that matters