I know I had Informants on everyone prior to the last couple of days. I know I lost my informant on AllMightyEmu, because I saw the event. However I am now missing an informant on Alruin, and I can't discern the cause of this. I also can't remember if I had the Informant still prior to the land exchange that just occurred today.
Hosted informants and agents are unique in that they hide in the buildings of your land (and are vulnerable to damage there), but along with diplomats are considered part of your battle mine and will follow you on land exchange.
If they'd follow you, it's understood that they'd follow anybody through land exchange right?
My opinion is that informants and agents should stay in their assigned plot of land no matter what, as long as:
-they don't fail a building destroyed survival check -they don't fail a mission survival check -they are not omniscienced
And diplomats should stay with their host player no matter what until there are hostilities