Oh goodness, poor Jasper.
Yes do try and let him see or hear you by phone or FaceTime/Skype etc. I used to do this when ai was in hospital to help settle my Chiko at night, and in the morning, so he knew his flock ate was around somewhere,
Get them to try a favourite piece of fruit or vegetable, grape and sugar snap peas are favourites here.
How long has this been going on for?
Wishing you well and hope you are back home soon xx