This document should be more than you need on the movements and actions of this battalion.
http://mississippiscv.org/MS_Units/18th_Bn_MS_CAV.htm

If a Confederate soldier ever fell into enemy hands, prisoner-of-war records will appear in his service file. In their absence, you should conclude that he was never captured. As you probably know, soldiers surrendered by General Taylor were generally shocked and disappointed when they learned of his agreement at Citronelle. They first learned about it shortly after Taylor returned from his meeting near Mobile AL.