Well, other than you mis-quoted me, I said 48 hours, not 24, I also very clearly said “along with all the instructions/ information you need”. I’ve been to that website quite a few times, it’s extremely clear about what you have to do.
BTW, even though the OP said they weren’t necessarily doing it, driving to the border and asking might be problematic since they’re in Tucson AZ so the nearest border crossing, Sweet Grass MT, is about 1,500 miles north of them.
I suspect a fax, maybe a follow up phone call out of an abundance of caution, would be a little easier.......