sure sounds like a backup to me. as to whether this is their fault or not, who can say. septic tanks are pumped dry of liquids and solids, but within DAYS they fill back up 100%. they must be full to work. the reason for pumping is that when they get overfull of solids the lines can no longer drain.

i wonder if your field drain lines were clogged, you pumped it, then when it filled back up it backed up again.

Since this problem is in a basement, any chance you have a sewage pump failure? It's not a pump in the septic tank but a pump that carries the waste 'to' the septic tank.
It should have had some type of alarm!

Thanks for your responses. It turns out it was a clogged main pipe from the house. I watched as they snaked it out and all the liquid came pouring out of the pipe from the backed up tub and toilet. Guess it was just a coincidence that it happened soon after I got the septic pumped.

What prompted the pump-out of the septic tank?