It is hard to believe that they hadn‘t heard neither this song nor about DS before!
I don't find it hard to believe since it's like nobody knows who MK is. Or DS... Unfortunately. Their music is famous, but not Pink Floyd or The Beatles famous, if you know what I mean. When I was 14-15 I've heard everything from The Doors to Floyds, Lynyrds, Sabbaths, you name it. But I never heard about Dire Straits.
Today, when I say "I do some stuff on YouTube, only 10k subs, not a big deal", people say "what exactly you're doing on YouTube?". "Mark Knopfler lessons mostly", I usually say. And they like: Mark who???