4th Gen Move effectiveness glitch?

[Thunderpunch]

I was fighting a wild weepinbell, using a fearow, and the weepinbell used razor leaf twice. Each time, there was no "not very effective" message, the razor leaf did regular damage, complete with the regular damage impact sound. How is that possible, when grass type moves are supposed to be not very effective against flying types? Neither pokemon's ability (keen eye, chlorophyll) should have any impact. Wild weepinbell cannot have hold items. Fearow was holding a lax incense (lowers enemy accuracy) which shouldn't affect that. Am I missing something or is it some sort of glitch/bug in the game?

 

[rndm.]

Did you use Roost with Fearow? It removes your Flying-type for the rest of the turn.

 

[Thunderpunch]

hmm.... I don't remember using it, but I must have, because that would explain it then. good call on that

 

[Thunderhead]

Woah, Roost disables the flying type for the turn?

That can explain why everything id duel typed, when matched with a flying type!

 

[The Doctor]

Yeah.

I made that mistake once.

Swampert And My Swellow on Emerald.

Swellow was low on health. I used Roost. Then i got Swampert to use earthquake ( these were the days when i know f*** all about pokemon type things ).

I managed to KO my Swellow.

Never Again..

 

[Weavile05]

I didn't know that until recently, but I never really use roost that much