OP, ups doesn't work on weekends, July 4th is a holiday so no monday work.
I don't know why it wasn't scanned on Friday. Like the above poster mentioned, it's likely on a rail car and will get scanned again tomorrow.
Best is to call the 1800 number and ask about Friday but it's not uncommon to have gaps in the middle of the week with no scans for 3 days when traveling cross country.
The fact.you have a rescheduled del date is a good thing.....too early to worry.