Queue problem...
… just call me … Tim :)
It’s unfortunately a weird glitch that has been around since launch and is hard to replicate (and therefore troubleshoot). If it happens again, use the in-game /bug report tool, which gives ANet extra data (such as world, time/date, instance, etc).
The silver lining is: you didn’t start at 78th and get re-queued to 43rd (which is what happened to me the last time I experienced this, about 2-3 years ago).
John Smith: “you should kill monsters, because killing monsters is awesome.”