Strange Job Offer Situation

Hey everyone, I hope I’m posting in the right place. I recently interviewed for a job I didn’t actually apply for—talk about a mix-up! I accidentally walked into the wrong office and ended up with a verbal offer. My start date is scheduled for tomorrow, but I still haven’t received any email regarding an official offer letter or the I-9 paperwork (just to clarify, I was told I would get it the same night I received the offer). Should I be worried? I understand it’s the weekend, and it’s possible the paperwork is just caught up somewhere, but I’m feeling a bit anxious about job security at this time of year. Any advice would be appreciated! Thanks!