Croatian/Slovenian Immigration

Could not be simpler crossing the borders via train here.  Again the train reaches the border station, pulls into a fenced off area, a large group of immigrations officers board and start scanning and stamping passports.  The first group passed through and stamped our exit visa for Croatia, and the next group followed closely behind stamping our entrance visas for Slovenia.  I didn't quite grasp it at first and kept reassuring the Slovenian officer that I already had a stamp and didn't need his.  Apparently I did.