Is it possible the client's lawyer lied to them? Or did the lawyer know he/she was misleading the court?
If the lawyer knows they are lying to the court, this could be misconduct and the law society (their regulator) can discipline them for it. But you need this proof which I'd be surprised if you had.
However, if the lawyer was lied to by the client, that's not something a lawyer can likely get in trouble for. The reality is every case involves two people with two different narratives, disciplining lawyers for putting forward different facts would lead to one lawyer always being in trouble... which doesn't make sense. Also, people lie, and lawyers aren't investigators.
Finally, even if you had evidence the person was not in rehab, this might not be sufficient. If there is an explanation that could reconcile your evidence with the client's assertion they are in rehab, the lawyer must take the latter unless it is obviously false.
Your remedy might be to bring it up at the next appearance and ask for costs for the previous wasted appearance. If costs were incurred. But the person to complain about is your ex, not the lawyer.
