Any sighting of the elusive Big Cat?

I think it seems pretty obvious by now that it's on a spawn timer from last kill / catch like area bosses rather than spawning at a set time. Presumably 24 hours.

Best way to test this is find one, catch or kill it, mark time and channel and head back 24 hours later. If it reappears then that's that.

Blue text appears on the ch when you cc into it. Doesn't matter how long the boss how spawned. Someone could be in the middle of hitting it, and you'll see the text. Test it out on an area boss to see proof.

This is false. As someone who has spent thousands of hours hunting bosses, I can definitively say that the spawn notice only comes up once and only for the first person to enter the map after it has spawned. People use this knowledge to their advantage at places like Seruf, by ccing through all channels before killing them. This discourages passerbys or potential hunters. Also makes the hunt a little more painful, especially if you aren't paying attention to what channels you've visited.