Still waiting on job offer letter

I hope I'm just being overly nervous about this...I accepted a verbal job offer at LTC the morning of July 18 and was told that I would receive a job offer letter outlining pay, hours, etc. as well as orientation and drug test dates. I went in for the "physical assessment" on Monday, July 21 as directed and passed (though I wasn't on his appointment list) and was given a document outlining what I need to bring to orientation (and verified the orientation schedule). I turned in notice at my current employer (office job--I'm a new grad) but have still not received the job offer letter. I called the hiring manager earlier this week to "check in" and let her know that everything was in place (including that I had scheduled my drug test based on info given during "physical assessment") and verify if I would receive my offer letter in the mail or if I would receive on the first day of orientation and was told "you'll receive it in the mail--thanks goodbye". Um, ok. Does anyone know if this is typical? I had three job offers and chose this place but am now wondering if I made the right decision...my orientation begins next week. I don't want to stress this if it's no big deal but in my previous job I drafted job offer letters on behalf of my boss before she offered the position (so they could be emailed and sent snail mail as soon as she hung up the phone). Is my perspective skewed? Is the job offer letter not so important in the nursing arena? I know that it's not a guarantee of employment but I know I would feel more comfortable if I had it in hand (false sense of security I guess?!). Thanks for any insight!!