No, they aren't, because there is no open market for private company shares.
You have a private company valuation you can base the share price on, but that's it. And even that is typically based on black magic and accounting tricks since, at the risk of repeating myself, there's no open market in which those shares are trading and thus no method for price discovery.
And any theoretical transfer of ownership would occur in a private transaction or on a private marketplace that specializes in matching buyers and sellers in private company shares.
<chopped this bit out since the dead horse is beaten>
Edit: And to provide something a bit more constructive, here: unless some lawyer comes up with something clever--and certainly it's worth exploring your options--my bet is your only real move is to just hold onto those shares and wait.
Eventually there may be a liquidity event--probably an acquisition--and hopefully you'll net out positive. You basically bought a 100k lottery ticket. I suspect all you can do now is move on and hope it pays off.