Only if the Senate allows proxy voting. Last session, the Senate only allowed proxy voting in committees, but not for floor votes. I don't know if the rules have been changed.
Don’t worry. Plenty of Senate RINOs will ‘reach across the aisle’ and ‘pair’ with Fetterman for floor votes. A Republican will abstain or be absent from voting so the end result is Fetterman’s absence will make no difference to the outcome.