A 50 pound bag of cement would only be about 2" thick, if dispersed in the footwell of a hot tub. There is rarely a drain in the floor of a tub. My sugestion is to drill a couple of holes in the cement, of a proper size for a cement anchor bolt, being careful not to drill deeper than the depth of the cement. Install the anchor bolts. Attach a chain to the bolts and yank. Use two men if necessary.
I'm not sure that this thread is lajit. I don't think that a customer would be that willing to scap the hot tub, unless the tub was full, with the pump running, when the cement was dumped.
There is a true story that happened in San Jose California, where a cement truck driver came home unexpectedly for lunch and found his bosses caddy in the driveway. He put over a yard of his bosses cement into his bosses caddy. The boss never pressed charges, but the guy was out of a job. Don't know what became of the wife.