There could be 2 scenarios in an asymmetric alow :-
Source A ------ SRX ------- Destination B
1) Traffic from A to B traverses through the SRX. Session would be created, no reply packets would be seen as the replies are taking a different path.
2) A to B does not traverse the SRX, however, the replies from B to A reach the SRX. For TCP traffic, the packets would be dropped saying "First packet not sync".
I do not think that security logs would be helpful to identify this as this can be seen in security flow traceoptions.
Please mark my response as Solution if it Helps, Kudos are Appreciated as well.