"Jeg troede du havde mistet flyet."
Translation:I thought you had lost the plane.
OK! Thanks. I've done a bit of reading since, and I think it would be something like "Jeg kom for sent til flyet". Would that be more correct?
Literally it's "I came too late for the plane", so yes, it makes perfect sense to use it if you missed the flight (because you were late, that is). I think that would be the best way to say it. You might also be able to use "gik glip af" or "missede" (loanword from English). You could also replace "flyet" with "flyafgangen" to refer directly to the fligt. I hope you never miss or lose any planes!
And "I hope your roof never falls down while you are inside". (Very common Irish greeting)