I'd probably do a cold reset on the unit. That usually fixes that problem when
I've replaced batteries if it fixed. Sometimes its a board issue but usually a
chord-i will fix it if you have it clean everything out of the unit. I suppose
if that didn't do it you might try a software reinstall.
If he pulled that small battery there's a good chance that you've lost
everything in the unit.
Tom
Tom Brennan KD5VIJ, CCC-A/SLP
web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html