When you wipe a mobile device that has a partnership with your Exchange environment, it might still be able to re-establish a connection and access the mailbox it had configured for 24 hours. This is the same as what happens with Outlook Web App and similar to when you disable an Active Directory account and the user can still use Outlook to access his/hers mailbox for up to 2 hours.
The solution to immediately prevent access to the mailbox after issuing a wipe is to:
1. Disable the mailbox;
2. Set a Send Prohibit Quota of 0KB;
3. Move the mailbox to another database.
If this is a mailbox in Office 365, then disable the protocols using the Set-CASMailbox cmdlet!