This is no clue at all.I also did another walk over of our ten acres today and no smells of decomposition or anything.
It's winter in your country, you said, the cold might not help in this matter.
In March, when it was still winter here in Italy, a feral cat was hit and killed by a car. The law asks us to call the environment office and report the roadkill to them, so they can send a person over to recover and dispose of the poor animal.
So I did, I called them five times over two weeks. I insisted because it was very unusual of them not coming.
Eventually, three weeks later, I did what they should have done. I went there, picked up the poor cat and buried him in a public green area.
To make this story short, three weeks after the accident that poor cat had no smell at all, and wasn't even decomposed, despite the fact he was exposed to the sun and the temperatures were raising day to day.
This said, I hope that all texts you are receiving can lead you to the finding of your Sebastian safe and sound!