I would be skeptical that this was the case. Unless Charlotte is telling us that she undertook 6 weeks of heavy combat training (< 5 hours sleep a day (broken by the ocassional 3 am drill), continuous repetitive physical labor in a chem warfare suit in a tropical environment). Furthermore, in this study testing occured after baseline only at week 4) - the results whilst significant statistically are not overtly high, at least to suggest one session of exercise could induce pain and this idea being causative.
Start with the simple explanations first. On occasion the crunching effort of a rowing machine where I lean forward can induce post-exercise pain in my TI (where I was diagnosed). However, it varies. One day, I can pump 30 minutes and have slight twinges in my gut - another day I rowed 1.5 hours (15 kilometers) and felt fantastic. If it was painful everytime, I wouldn't row, and would stick to the exercise bike.
One could hypothesise that the mechanical action might have induced this. It may not necessarily come up painful immediately. Furthermore, the exercise itself, especially squats, could have resulted in increased blood flow to your abdomen (muscles swell after exercise) which could have induced the pain by pressure. The fact the pain went away the next day as if nothing was wrong suggests this as a possible reason.
Furthermore, it has been shown that post-exercise, inflammatory mediators are raised, especially muscle building exercises - this also could be a reason. However, countering this are studies that long term exercise lowers overall inflammatory mediators. So don't take that as reason not to do these kinds of exercises
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Try the exercise again, but go lighter, build it up and stop if you get pain post-workout, and go back down to the lighter level/load/number of reps etc. Best of all, don't give up on finding the right exercises for you. I just need progress, not perfection, is what I always tell myself. Little steps
