Wouldn't you think John would be more traumatized by it (especially if he already has PTSD, though that's a little debatable.) And shouldn't he have injuries?

For a moment I thought John was sending the texts, pretending to be in danger to teach Sherlock a lesson.

Keep in mind that the texts weren't send to Sherlock, but to Mary, at least at first. She was the one who got the first texts and then came to Sherlock.

As for injuries: I suppose that John was rescued right on time, just smoke, no flames.
And I'm sure he'd eventually come to Sherlock, bonfire or not, but the bonfire might have been some sort of catalyst. Mary would have talked him round, I'm sure.

Marva wrote:

Yes I also think that he would have gone back to Sherlock, no matter what. When he got kidnapped he hang around 221B already. I think he wanted to go there but waited for a moment until he'd finally decide and then he got kidnapped.

Right, I completely forgot about that just now. So there's no doubt that he was on his way to Sherlock, even without the bonfire.
In the scene with Mary sitting on the bed and John not shaving for Sherlock Holmes (), I was already convinced that John would go and see Sherlock when Mary says "You're gonna go see him again?".

Have you see the little helicopter in the scene between the bonfire and 221B with Sherlock's parents?
I think there is even a muted sound of a helicopter.
Have a look at the sky.

I saw many funny comments on tumblr to please check your bonfires for John´s etc.. 

Did you know that fire is often used as a metaphor for love and passion?

Liberty wrote:

Yes.  It's a shame Sherlock pulled him out of it.

(I'm kidding ... seriously, I'm kidding.  Just couldn't resist .  

LOL

I just wanted to point out that only Sherlock went in. Mary stayed outside...