I sent my comm to a planet at the edge of the solar system That was on an elyptical orbit. What I didn't notice was that that the planet appeared to be stationary. When he reached the planet, he vanished. Pressing 'c' then 't' just made the invalid selection noise. Very strange.
I've had that too when I've sent things to planets. At least now with the additional window you can keep an eye on the destination planet. Fortunately it never happened with my commander, only with the construction bots.