After the scale puzzle and before the cobra puzzle, we're to return to tunnel three and move the coffin cover to see a mummy inside. When I get there the cover is off the coffin and no mummy. Did I miss something somewhere? The mummy is mentioned in the conversation with Jon Boyle later.

It might not be triggered yet.
But if you already talked to Jon about finding a mummy - no problem then.
Continue on or you can look again to see if it is there. Have fun.

That's just it. Ithe mummy comversation wasn't there. Do you have any idea what triggers it. I missed the Uncanny eggs in the Scarab puzzle.

The egg does not have anything to do with the gameplay - they are optional.

Ah - so in the talk with Jon; the mummy is still not there.
Then continue on and then later go back to see if you find a mummy. It might just be time between the cat room and finding the mummy.

Did you check the ceiling of the cat room?

You mean, did the two bird tiles go to the ceiling? Yes!!
Found the mummy!! Do I still have to talk to Jon about it?

Jon will tell you some info about that mummy then.

Thank you!!!

Have fun.