This is the only solution I can come up with

Code (Text):

1. on place:
2.    add location of event-block to {playerblocks::*}
3.  
4. on break:
5.     if {playerblocks::*} contains location of event-block:
6.         send "block placed by player"
7.     else:
8.         send "block not placed by player"
9.     remove location of event-block from {playerblocks::*}
10.  
11. command /removeplayerblocks [<text>]:
12.     trigger:
13.         loop {playerblocks::*}:
14.             set block at loop-value to air
15.         send "All blocks placed by players got removed"
16.  

Not tested, not sure if it works