Obstruction?-Nothing?

[chuckfan1]

Had a play this past weekend, and would like some feedback. Surprised I havnt had this happen more often, considering how often this type play unfolds:
R3, R1. R1 stealing on the pitch. F2 comes up firing, throwing to F4 moving in a straight line towards home, in case R3 decides to break for home.
F4, R1 and ball all come together in the same spot. R1 bumps into F4 as ball caroms off F4 glove. Due to F4 charging in to get the throw, F4 was in the baseline.
Now, having never seen this happen, I thought it was nothing. I guess one of those "train wrecks" that due happen. And my thinking that the fielder was "protected".
My partner called obstruction. Put R1 on 2nd, and kept R3 on 3rd, saying that R3 never attempted for home, and likely wouldnt have scored. He later explained to me that the Defensive coach wanted interference. My partner also told the def coach that the offense is protected on that play. When the coach asked why, partner said.."well who put the ball there?".....
But I keep thinking isnt this the same as a throw coming into 2nd base and ball runner and fielder all arrive at the same time? And its "nothing"? I knew it couldnt be interference on a thrown ball as that has to be intentional.
Unless due to the fact F4 charging into path of R1 makes it obstruction?
Im just surprised I havnt seen this before, as often as that play unfolds, especially at the youth level. Anyone?