There are four different things you need to think about in a situation such as this one.
1. Given the distance from the LOC, a competently designed and run mission profile by a low flying aircraft packet can enter PK undetected, use the terrain in its advantage, release weapons and get back over the LOC in something like 5 minutes. Even less possibly.
2. The defensive force can react to such a mission after it detects the packet. Given the distances and the terrain involved, this may have or have not happened by the time the planes were back in IK.
3. Detecting the force is one thing. Intercepting it is another all-together. Again, given the approximate time the packet stayed inside PK, it is prudent to assume that the margins were very tight for any defending force.
4. Even if the force was intercepted, you also need a clear RoI doctrine applicable at the time of said interception. This may or may have not been in place. If the defending force needed high command authorization to dispatch weapons and the outstanding RoI was to warn first, it is possible that the attacking force was well over the LOC when said authorization could have arrived.