I agree, I also got into a needless flap over not very much.
For a blockage at the neck of the day bag, I think a reasonable self-help emergency procedure is to pull off the tube where it feeds into the bag. Which is what I tried to do, and punctured the tube -- it was wedged on solidly. I ended up cutting it off with a sharp knife and shortening the tube slightly. I felt reasonably confident doing that as the tube I had was designed to be trimmed back to suit leg length and bag configuration -- maybe all are like that.
With the bag disconnected, it then should be a fairly easy matter to flush or back-flush the bag and remove any debris from the neck of the bag -- I didn't actually try this.
If you have the bag disconnected, and over time, there is still no urine coming out the open tube attached to your catheter, then you need medical help. You probably have a catheter blockage. I believe back-flushing works there too, but you need someone to help who knows what they are doing -- at least for the first time.