if all else fails, contact the IRS? (saying "I've been told that [person X] is holding [financial resources Y] in my name, but am unable to get further information and I'm concerned about my own tax liability")

and before that, just oh-so-casually (or not) mention to that person that you're going to have to report to and get the information from the IRS if you don't get that information within, say, 5 business days.

just a thought...