@Steve O. you need to see the report that it came back clean, but I'm a little confused as to what happened. When the tank is removed, it is either a leak or no leak per the town when the come out. If the town confirms there is leakage, you have to run the tests and do remediation. That test could come up clean. The town has to fail the tank when there are any holes that could have had leakage and when they remove and scrape the tank sometimes they make pinholes when doing it. The whole thing is a racket for some companies, but there are good ones.
I've never heard of a one-person tank removal company. It's not possible. How much total did you pay? Was there any remediation required and was it done? What paperwork have you received so far? To close everything you will need a NFA from the town saying that No Further Action is necessary on the tank. That's what you will need to sell the house eventually. Give me some more info on the costs. It could be ok, but there are a few fishy parts here.