This is the second scope I've bought (in my modest collection of a half dozen used cheapies) that did not have its dew shield. In this case, an early 60's Mayflower 60x700 in its original box. Everything else was there, including the eyepiece extension tube, finder scope, handles for the mount...everything except the dew shield. Oh and the tripod legs, they were gone too.
How? The scope had a box, made to fit everything (just barely, but that's a different rant). How does something like that just...disappear? (Or the legs)
The same problem occurs with guitar amplifier foot switches. I mean, amps have a handy little spot in back perfectly situated to set the foot switch in. You unplug the footswitch from the back of the amp and set it in the convenient cubbyhole that's right there! Yet practically every old amp I come across that requires a unique footswitch...is missing it. They won't fit other amps. They aren't for sale on evilbay. There's no coveted black market for Peavey Classic 60 foot switches.
Maybe there's a secret alien base behind Area 51 that collects dew shields, guitar footswitches, and the occasional set of tripod legs.