So apparently, it is possible to get stuck in the cave with the poor mummified Templar. Khan never showed up for me. I didn't pay attention, but it might have been that I read the inscription before I looked at the statue.

Now I'm going to curse and start the game over sometime when the rage fades.

You only had one save? Blimey!

He came in for me when I checked the inscription, even if I did little else before.

Are you sure it was a bug, you only mention two objects; did you do all three things you should in the cavern? (get the lens, examine the wall, look at the statue)

Yes, got the lens. I checked and double checked a walktrough before determining I was stuck. =p

I found stupidly hard that you had to look at the statue with the right mouse button, the left button doesn´t work. I know for sure, because the cutscene unlocked after pressing on that statue with the right button, left one didn´t work.

This. This is correct.

I just played through it, and had the same trouble.

But it isn't a bug, just a weird design decision.

For some reason, the developers put an "interactive object" gear mouse over icon on the statue even though you don't use it for anything instead of just an eye or magnifying glass icon for examining it. So you have to press the right mouse button to examine it, like other interactive items or items in your inventory.

The cursor does show this, with gears on the left and an eye on the right, although it isn't exactly the clearest thing.

...come to think of it, I think I vaguely remember running into the same problem the first time I played the game, in the terrible GBA version.