Responsive display issue

My guess is that this is a theme specific issue, but on the off chance it isn’t, I thought I’d post here. (I’ve been trying to get an answer from Themegrill for over a week now but there have been communication, technical and time zone issues.)

When I test the responsiveness of our site by shrinking the browser window on my desktop computer I can easily see how it should display on a handheld. But when I pull it up on an actual handheld, I get a miniature version of the desktop display (no hamburger, no single column!)

here’s our site (under development): http://www.uproc.lib.mi.us/pwplinfo/