There certainly could have been other contact missions taking place; maybe when they’d pulled up stakes they’d grabbed every one of their interpreters.  It stood to reason that they might have been smart enough to not put all their eggs in one basket; for all he knew, the building he now found himself in could be filled with other people.  At his very best, he figured he was only average when it came to learning a new language—and that was if they’d picked humans randomly.  Maybe that was why the delay after he’d first encountered them—maybe they needed time to find other, more promising recruits.