In Blackbaud Grantmaking there is no way to undo the deletion of a contact record.

In GIFTS ALTA that is also the case unless you can obtain a backup of the GIFTS database.  As the GIFTS software is installed and hosted by you, your IT team can restore a backup from before the contact was deleted.  Please note restoring the database means any updates or changes made to the database after the update will need to be recreated in the restored backup of the database.