IOLTA accounts sometimes contain unearned fees; it would not be uncommon for an attorney to write a check on an IOLTA account to pay himself or herself; i.e. it's not automatically suspect.
You process third party claims against property owned by the garnishee. According to the title, the funds in an IOLTA account do not belong to the attorney; the account would not normally be subject to garnishment. At the same time, an attorney avoiding creditors would be smart enough to know that and could hide his personal funds in this manner.
Research the deposits and withdrawals from the account. Show the activity to your bank counsel and see what she thinks is happening. If the IOLTA is a sham, your attorney may say it is subject to the garnishment.
_________________________
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.