Have phase and triggered waveform download scripts use event web service for filtering

Instead of searching using the indexes, which search by event id will cause download of all files - use the SCEDC FDSN webservice. https://service.scedc.caltech.edu/fdsnws/event/1/  You could query either by url - or use obspy Client.  
You should use format = text - I think that is the fastest result since you are just looking for date, mag, lat/lon information