I need an Lawyer but I do not know the area od practice I should be looking for.

I am 62 years of age and decided to cash out my 401 to do some repairs around the house and pay some debt I had. I contacted my employer and asked for disbursement. I filed the required forms and I was told I would receive a check in a couple of days. Two days later I received a check and I cashed it. This was a month or so ago. I received a phone call from the carrier and was informed the check was pulled on the wrong account and I needed to return the money immediately. I stated I wanted something in writing before I would even consider this problem. If this is real I have a problem as I have spent some of the money and do not have funds to replace it. I do not want the money if it is not rightfully mine but it appears that I might have a major debt to repay and it was not by my own doing. This could be devastation to our home and finances. What course of action do I have and what type of Lawyer should I be contacting? I need an lawyer to help me get through this. Thank you