Hey, listen to Mo! Don't give up hope. They seem to pop up when you least expect. I lost my snake a total of 3 times (only one of them was actually my fault).
Once he crawled into a hole in a wall and didn't come out for two weeks.
Another time he crawled down a sink drain and didn't come up for 3 weeks. (He poppedu p in a sink in another room)
Last but not least he crawled out of his tank while i left the screen cover open for "just a minute" and he disappeared somewhere in my room.
BUT I found him even after all that AND he is still alive. So don't lose hope and turn the lights on randomly at odd hours of the night to see if you can find him roaming around in the dark.
What I did the third tiime was I took an empty tissue box, poked a few holes with a pencil and put 2 pinkies inside. My baby crawled in and had a nice meal and decided he'd rather stay in there than go back outside to digest his meal. I checked these little boxes 3 times a day and voila! there he was 3 days after I lost him. (he was really small at the time..maybe 13 inches and very thin so he could fit into the pencil holes)
so...yeah..what I meant to say is don't give up. in a roundabout way.
Irwin is a beauty and I hope you find him. Maybe you should get a more secure tank for him next time...?
Best of luck!