"PATROL" is the same as .NULL.???

I have a departments table, and when I open it in browse mode, and type the following:

BROWSE FOR vehdept = 'PATROL'

It pulls up a single record, which has .NULL. in the vehdept field. There are other records with .NULL. in that field, but it only pulls up this one. ? IsnNull(VehDept) returns .t., so it's not a case of a string ".NULL." (Which shouldn't match either.)

Luckily, this isn't anything I was actually working on, just something I came across while trying to transfer data. But.... any ideas what could cause this?