go to your garrisons and recall them (if you want them back instantly )

note that they are still collecting rations thats why they are yet to return :))

Sent 6.5k Units to gather rations. Left alliance i was in and teleported to new location and joined new alliance. Units still haven't returned. Says I have 6.5k out

If you don't see you Units in Garrisons, it means that they have returned.