Sounds like a problem with the hydraulic clutch mechanism. I’ll bet you’ll find a puddle of brake fluid under your car and/or no fluid in the clutch resevior. First I’d give the system an eye-balling to check for any obvious leaks, especially on the rubber hose(s). After that, try refilling it and bleeding it at the slave cylinder and then have an assistant pump the clutch in while you look at the components to try and find the leak. It shouldn’t be a big deal-- the rubber hose and the slave cylinder are the most likely culprits and they’ll shouldn’t cost much more than 30 bucks or so.
Did you ever get the alternator out?