Sid,
I had my 4 month old Puget in a 10 gallon Viv with some other juvenile 4-5 month old Butler's and Eastern's, when one day I noticed my little Puget was gone. Like you, their water dish and over priced cave were placed low so I didn't think there was anyway for her to escape...
Could not see any huge bulges in my Butler's or Eastern's signifying that they ate my little Puget. I was certain that there was NO WAY my Puget could climb out of the 10 gallon Viv with the screen-top? All right... who ate the Puget? (No basement TV watching for you guys for 1 month, little b*stards)
About 3 weeks later, I heard a noise in my 3ft. tall trash can, next to my workbench. I look in the trash can and there's my little dehydrated Puget....!
I think if they get wet from their water bowl they can shimmee up the sides of the glass tank and, in my case, wedge themselves under the screen top and play a month long game of hide and seek with me..
Sorry to be long winded... But, I strongly believe your snake went AWOL and was not eaten by his pals...
Gotta believe you could could really identify if one of your snakes ate 3 juvy Garters.
Please let us know if you find them.
Regards,
Jack