Physiological factors - possible blame for seizure?

I'm really confused and based on some of the comments I've read on this site, this is indeed a very mysterious topic. I was rushed to the ED last weekend after losing conciousness in a department store (was by myself). The EMTs claim that I had a seizure (based at least in part on witness accounts) and the ED doctor seemed to support that. The neurologist that I'm now seeing has ordered an MRI and EEG, and doesn't seem to be concluding anything himself. I have my own theories, but nobody seems to credit them. The fact is that I had just played 2.5 hours of very competitive tennis in the very hot sun, and despite doing my best to stay hydrated and cool, I was probably somewhat overheated and dehydrated (or at least suffering some form of electrolyte imbalance). The cramping in my calves and weakness I was feeling out of a need to eat are both familiar signs for me after agressive play in the heat. Normally I cool down and then eat and drink to replenish, but on this day decided to run into the store first for some things I needed. It wasn't long after entering the store that I realized I was in trouble. My weakness increased and my vision became very impaired (kind of like looking out of a kaleidescope). The vision impairment is something I had experienced twice previously, both times after spending several hours playing tennis in extreme heat. Both times previously I was able to overcome the temporary vision impairment simply by sitting down. This time though I could find no place to sit and instead just leaned my arms and shoulders on a display shelf in the store. Next thing I knew, I was regaining conciousness on the floor with the EMTs over me. Part of my dilemna now is figuring out the sequence of events and what might be reasonable conclusions. The ED reported my blood work as being normal, but is that partly because the EMTs had given me an IV? Even without an IV, don't our bodies produce adreniline in reaction to events like this, which in turn can bring our blood sugar back to normal in a hurry? Also, what about sodium levels? If the IV that was administered had a saline solution, then I'm assuming my sodium levels would have been back to normal by the time anybody checked. I also read somewhere that during the "cooling down" period of heat exhaustion / heat stroke, seizures can be experienced. At 49, my Mother reminds me that I simply shouldn't be doing the kind of stuff I do anymore. Perhaps she is right, but I'm not convinced that I can't just work harder to prepare myself for extensive physical activity in the heat. I'm not sure what's going to happen now though. Assuming that nothing shows up on the EEG or MRI, will the Neurologist just wait to see if I have another "seizure"? Or am I being too stubborn and should I be viewing my earlier 2 vision episodes as some form of seizures themselves? Guess I'll wait to hear what the Neuro has to say, but any advise or comments will be appreciated. Thanks