Oppose the garnishment. There is a problem by either the attorney or the collection agency that they need to resolve.

You could sue them. Depending on the amount at issue and the importance of resolution, it may or may not be worth proceeding.

Probably but a motion to reopen may work. But if they do so they may meet with a statute of limitations defense.

In most instances, yes, unless there is a specific statute or regulation for that particular industry.

Check court records to see if you have been sued or check your credit report.

Yes and the client can move to dismiss subject to that clause. Note, you might lose certain rights by failure to first pursue the matter through...

The State Bar may be able to assist in getting your file.

Not unless the fee agreement included this.

I think asking the client’s opinions and seeking client’s input shows good legal skills.

Consult with experienced criminal law appellate attorneys in the state where this occurred.