When firing arrows into TNT, and it subsequently priming and exploding, the arrows persist in the location of the original TNT block.
Steps to reproduce:
1. Place TNT above ground as shown in picture.
2. Ignite with flame bow.
3. Watch the arrow bounce away and then come back.
Placing TNT back into that location will immediately ignite because of the persistent arrow until it despawns
Was able to reproduce, even without the iron bars. Flaming arrows sometimes persist on TNT blocks.
Edit: It is an actual arrow (you can pick it up).