[chernevik]

That doesn't sound even remotely close to right.

If the client is the owner of record Mercury hasn't any claim at all.

[jqpabc123]

My guess, this is a trust/FBO co-mingled type account of some sort.

Only Mercury knows the exact structural details but based solely on their statement above, they have significant control and claims that you can't easily override yourself.

I wouldn't count on this all being resolved quickly in the event of a bankruptcy.