Doer, that happened to mine when I changed from Low to Very High graphic settings (for a screenie).
The miniature icon remained when I returned to Low until the VU, after which it went back to the standard size.
Whew i was worried when i saw it after i left it out just before the VU that it had permanently shrunk in the rain.
Kind of like it like that actually.
Remember when armor bits etc. used to go back and forth in size from one VU to another? If you had your armor arranged in the tab it would end up a jumble.