sick pay is at the decretion of the company in most cases so you don't have to pay him
one of the guys who was sacked at our place recently was told that he was having too many days off sick so he wouldn't be getting paid for them, he had 55 last year and 48 the year before and the ocmpany only pays for 8 weeks sick IF you're off for 8 weeks on the trot (i was off for 5 or 6 but it was all documented that i was sat at home with pipes sticking out) but this guy would phone up on a monday and say he was sick and then come in for a few days and then call in sick again
i'd cut him some slack, mentin it to someone that you've seen him in maccy d's and let the word get out
obviously, if he doens't come in tomorrow then give him a call and find out whats wrong with him