I'm a bit confused, so I'm going to ask some clarifying questions.
When you say the mag catch, do you mean the part the holds the mag in the gun...the mag release?
..are you saying that it is secured in the gun until you pull the slide to the rear...rack the slide?
...how did you determine that it was caused by the recoil guide rod?
...if you are referring to the rod that is surrounded by the recoil spring, it has no interaction with the magazine or the magazine catch
...I'm not sure which point it might be missing, can you post a picture?
...nothing on the guide rod has anything to do with the trigger's operation
...are you trying to dryfire without a mag inserted?...the S&W semi-automatics come equipped with a magazine safety which prevents the gun from firing when a mag is not inserted
...did your gun come with the owners manual and have you read it?...all these things are cover in the manual