It is a digital recording.

Then it's not Hi8, it's Digital 8.
Typically a very robust format and almost impossible to erase with a magnetic field. Are you playing this in the correct type of VCR?
A D8 tape will ONLY play in a D8 VCR or camera.
A D8 VCR or camera will play Hi8 and Video8 but not the other way around.

Bob.

The tape is a Hi8 tape, and actually I'm not sure if it was recorded with a Hi8 or Digital8 camcorder. (it was my cousin-in-law's)

I'm trying to play it back in a Digital8 camcorder, which I've been able to play back Hi8 tapes that were recorded on it before.

OK, then a D8 camcorder *should* be able to play it back regardless of what it is. Of course the D8 camcorder could be faulty, have you tried another tape just to ensure the camcorder is still functional.

Also check one of the menu options "A/V->DV OUT", I'm 99% certain that will not stop a tape from playing onto the local LCD but worth a check.

Bob.

The D8 camcorder plays other tapes, just tried earlier as well.

I'll confess that the "bad" Hi8 tape in question had been under my car seat for six years.

My cousin-in-law recorded my wedding, his wife's pregnancy, and my late grandfathers last words (on tape). I guess I put the tape in my car way back when, and forgot about it. My car recently died, and I was going through it getting stuff out of it and found it....

OH!
Six years in a car, the heat might not have done it much good at all.
Try spooling it a few time, that's about all you can do and I've not come across anyone doing archival retrieval on D8. One problem is if the tape stretches or bows the heads cannot track the tape and it's impossible to get them to. What should have been a series of short straight segments written diagonally across the tape become bowed and no one that I've heard of has found a way to make a head move in that fashion.

Good luck.