I believe my mechanic almost screwed up my car lol check it out?

lacking that seal would allow unmetered air into the engine and the air fuel ratio would be off. the engine could struggle to run and would lack power. a CEL could come on. if that seal were to fall into the engine, it would gradually be drawn into the engine maybe and if it did make it past the valve, it might keep that valve from closing and you would have a noticeable miss.