Our Beloved Burt, Passed away suddenly on December 30 Options

[Scott&Senka]

We are so heart broken since Sunday when we learned that our beloved cat Burt passed away. We went on a ski vacation to Lake Tahoe and on the way back received a call from petsitter that she found him dead that morning in his box. I was in absolute shock, started crying, could't stop, it was horrible. We left on December 26, Burt was fine, a little sad but o.k. We found this petsitter who made us sign all kind of agreements, and she seemed professional, recommended to me from a reliable source. She said that she will leave a report card for each day. We don't know what happened. On the checklist it seemed that she did everything except giving him treats, which we specifically asked for and made a big deal of, since he was used to that every day. He is just gone, and it is so hard to believe. My husband had him for 8 years, got him when he was very little. We could have never expected this, he wasn't that old. We had a funeral for him on New Year's Eve in Victorville in my husbands parents' garden. It was a very sad ceremony, but we are glad we know where he is. We marked his little grave with Love and Peace Christmas ornaments, and lit a candle.
The only thing we noticed lately, was that it took him a little longer to eat if we offered him a little bit of fish or something, and he would have a bit of a gag reflex before eating, but we didn't think it is anything serious. Scott said that a couple of days before we left Burt was trying to jump on the couch, but missed it, but at the time we didn't think it's a big deal. Anyone knows what any of these symptoms could have indicated?
We are so sad, it's hard to put in words. We just hope he is o.k.
Our hearts go out to all of you who lost their beloved pets.

Senka and Scott