In electrofishing there a number of times, we had never found an overall shortage of trout in the upper half of the specific stretch that you fished, although the population adjacent to the ball fields, etc in the park had been surprisingly limited at times. That has made me wonder about C&R mortality of freshly stocked fingerlings in the park because there has been a lot of evidence of bait angling over the years, probably by kids, seen there in the summer....bait containers, spilled corn, etc. That is the reason why an original fingerling stocking point was moved a short distance away from the park after 15 yrs.
The stretch from the RR bridge down to Rt 443 has never been electrofished although there has been more than adequate time for annual stockings to populate that segment since around 2001. There are fishable numbers of trout in individual spots down from Rt 443 so as long as the trout find the habitat to be suitable, the same should be true from the RR bridge down to Rt 443. There are also some wild brook and brown trout in the stretch that you fished, so I would chalk your experience up to a bad day. It happens.
I too have soft spots for any recovering rivers, streams, and estuaries. I maintain a strong interest in the upper Schuylkill.