Whenever Shir is in your party, and you enter a shop or a certain location in Phantasy Star II, there are rare occasions when she will just disappear. Returning to your home in Paseo, she will show up again. If the party inventory was empty, you will see an item appropriate to the shop or location which she apparently stole from.
You can just enter and exist shops repeatedly, driving people who are watching you play mad.
This technique used at a certain location is how you get arguably one of the most important items in the game, the visiphone, which allows you to save anywhere, as opposed to Data Saving stations!