I live overseas and two friends from home have recently had birthdays - sent one flowers and one a small gift. I could track the delivery of both so knew they’d been delivered but didn’t get an acknowledgment or thank you until I followed up to ‘check’ they’d got them between 1-2 days later.
If someone sends me something I message to say thank you as soon as I get it!
Possibly expecting too much to do happy to be told IABU.