If you look at the time line Aang says on arival at ba sing se he knows that appa is there.
But when you look to appa's lost days you see that appa arives more then a day after Aang arrives.
or is it just an illusion in my mind?

I Agree with MCMLXVI, its just Aang expressing his new found feelings of hope, if you follow Appas lost days chronologically, appa meets suki after she returns from serpents pass, after that it takes them a couple days to get appa back to full health, then he flys to the eastern air temple, then back to ba sing se which shuld take??a couple more days.

I think that was designed to be two big shocks instead of one: Long Feng has Appa(which for some isn't that big a shock) and that Appa didn't get to Ba Sing Se until AFTER Aang got there, so all their searching and questioning was pointless

Also, how did NOBODY notice the big flying bison and then the big BOOM when Long Feng grabbed him?? I know the citizens were supposed to be scared and all, but Appa is about 10 times bigger than the kids, and about as big as half of the houses there...What was it "Keep-Your-Head-Down" day??

Another interesting thing was when Aang used the whistle for the animals.?? He sent out a huge wave that attracted all the animals including someone's house cat.

Then again, secrets and conspiracies work 300% better when scripted. I'm sure that in Hollywood, even Reaganomics works.