There's probably not a future in greeting cards for me

I got a sympathy card at my desk today.
 
No, it wasn’t presented to me as the recipient of the sympathy – it was a card that was being routed to everyone in my department to sign for someone else. Our department has between 60 and 75 people, and I only work directly with about 10 of them. The rest are mostly just “say hello in the hall” people, with whom I have no real business or personal relationships. The recipient of the card is one of those folks, and he lost his grandfather recently. I was unaware of his loss until I got the card at my desk.
 
So, like a good coworker, I wrote, “Sorry for your loss,” just like five or six others had, but I was really wondering what else I could have said that didn’t sound completely awkward. Of course, since I am not from around here, and I am acquainted with very few of the locals, there’s really no chance that I would ever have met this coworker’s grandfather, except by sheer coincidence. There was really nothing else I could have said besides those four words.
 
Then I began to think of inappropriate things I could have written that would have made future hallway “Hi how are ya” moments much more awkward:
 
“Terribly sorry for your loss. Pappy was a patient man who helped me out of many a sticky situation down at the track.”
 
“Coworker: Please accept this handmade coupon for a free hug, no expiration date.”
 
“So sorry for your loss. Hope you get some good stuff, like a pool table or a classic car.”
 
“I’m sorry for your loss. Also, I’m sorry I ate your bologna sandwich out of the fridge last week.”
 
“I’m sorry about your grandfather. I wish I could tell you about his Vegas trip in ’79, but he swore me to secrecy.”
 
“Happy birthday.”