I'd be curious to know what "WiFi" means here exactly. If it means "my flight plan is stored on the internet and I didn't save a local copy" then yeah, I think that's insane. But if it's a local WiFi network it doesn't seem so weird to me. You should, in the course of day to day operation, be able to expect a WiFi router will work.

Of course, it'll fail at some point, but it's not like they were cut off from the world, they could have radioed for the information if the copilot didn't have it, or something.