It's better not to leave the disc in the drive, but if it worked for an install, it sounds like you didn't do any damage this time. The risk isn't so much one of damaging the disc, as it is the chance of damaging the drive - the laser read head is fragile.
Off course you should try to refrain from leaving media in drives when moving, but if so the chances of damaging parts is next to 0 unless you go frantic with the case.
And yes the laser head is fragile, but still needs to suffer a direct hit on the glass part or it's suspension for immediate damage and that is very difficult for parts loose in the drive.
For example, i have seen drives that had media shattered to bit's in the drive itself under high speed rotation and the lens suffered no damage at all.