Note: Not sure if this belongs in another sub, happy to post elsewhere.

I'm a software engineering team lead and a few month ago my team hired a new developer. The person we hired interviewed well and seemed really knowledgeable on technologies we use. During the interview he came on camera and nothing seemed weird about it. We discussed, decided he was the most qualified and hired him.

Fast forward about a month and a half, the dev says he needs to take a few days off (does not say what for). I tell him that they will be unpaid since we don't allow paid time off in the first 90 days. He says thats fine and takes the days off. Later when asked he said the days off were for an "Eid feast". Googling it made it seem like that should've been in April but he took the days off in June.

The day he comes back I immediately notice his voice sounds different during our standup. I'm thrown off but continue as normal. I check with a guy on my team asking if he sounds different. He says he didn't notice a difference but will try to pay more attention to how he sounds on calls. A little later he does say he hears a difference but I wasn't sure if it was just suggestion bias.

As time goes on he seems less articulate and put together then he did the first month or so. Performance-wise he's getting some things done but his tickets have not been terribly complex. I had been trying to ease him into our systems because there's a lot of context to take in. However, in general he does seem more nervous, unsure, less well spoken. There's been a few instances of him claiming he understood something but having to walk things back a bit. Overall, he's not performing quite at the level I expected (senior engineer), but he's been doing ok so its been hard for me to let him go purely based on performance.

I shared some of my suspicions with my direct manager and also noted to him that when i hover over his name in teams it says "same timezone as you" even though he claims to be in a timezone 3 hrs ahead. Since that conversation my manager has come back to me and said a few others have mentioned separately that he sounds different. The guy has not been on camera once since the vacation and my manager said when he tried to get him on camera he claimed he had family around or his house was messy.

I went back and reviewed his resume and the details on it have some vagueness. The area code on the phone number is from new york (he said he's from florida). There's no socials liked linkedin or anything. No address information. His email listed starts with the word "tech" which i thought was a little weird.

I had a friend recently say that they had heard of fake candidates "swapping" after a vacation early after being added to a team which made me feel less crazy but I still don't know if there's a reasonable explanation for why this guy seems different.

Questions:

Am I crazy?

How common is this scam? (I've read more about people showing up as someone else on the first day, not two months in after a "vacation")

How do I go about confirming if this is actually the guy I hired? (I don't want to cause drama or issues if there's a reasonable explanation)

Extra context:

I got promoted to a team lead in January so I've been adjusting to a lot of different changes in responsibility and this is one of the last issues I wanted to deal with.

I'm also a little annoyed because I had a friend that applied for the position that we probably would've hired, but he was less experienced than this guy (at least it seemed that way) and the two team members i had in the interview felt the same way. My friend got a job elsewhere so it worked out but would've loved to have brought him on.