Does non-magical interogation exist in 3.5?

Can you make use of your skills in heal (so you know what parts of the body wil hurt the most without them dying), together with diplomacy (to convince them to see your 'point' of view), and have them make a will save to avoid telling all?

Or you can skip all that and just go for the KODT method of a 'Buring torch to the groin'

If that fails (or isn't to your taste) maybe you can use the speak with dead spell? The spell description does say that the "Answers are usually brief, cryptic, or repetitive", but the PC can't resist it if they manage to get a cleric with a the same alignment "If the creature’s alignment was different from yours, the corpse gets a Will save to resist the spell as if it were alive."

Heck, since the PC "can’t even remember being questioned", they could kill him ask him questions and there's no way the party would know what info he has given up.