You could always setup a video camera like we did when you are gone. We just found Yoda sleeping the time away (for 60 minutes until the tape ran out)... When he was a baby, he was VERY depressed when we would leave him, now it seems that he at least accepts it, but not like he likes it or anything. When we come home and open the sliding door to the kitchen, he jumps up and licks us and his tail goes 60mph.
