Long-codes (TF# and 10-DLCs) behave differently than short-codes when it comes to STOP replies.
The messaging aggregator controls and responds to stop requests on TF#s and 10-DLCs.
As a result, a contact's STOP request will appear in an account's received log, and the contact will be opted-out of messaging, but the aggregator's response will not appear in the sent log.
In order for a contact to opt back in to messaging they must reply to the stop message they received with the word UNSTOP.
Sample 10-DLC STOP reply from the aggregator:
Sample 10-DLC UNSTOP reply from the aggregator:
Sample TF# STOP reply from the aggregator:
Sample TF# UNSTOP reply from the aggregator: