If it had an appropriate bromide bank, then draining down to a foot and refilling won't dissipate it enough. Typically one adds a 30 ppm bank of sodium bromide, and then if tablets were used it would have likely increased. A pool that size drained down to 1 foot would only dilute it by about 75%, leaving about 7 ppm of bromide. That would still make it a bromine pool.
Unfortunately, there's no way to know if they actually added the bank or just put tablets in. Also no way to know if they added a bank and then used a bunch of tablets. It would be a fair amount of work, but I would add a foot of water, stir, and then drain the foot 2-3 times. This would dilute any bromide and whatever else is in there enough to hopefully not cause any issues going forward. I hate to suggest dumping thousands more gallons of water, but without knowing what is in the water I would want to get as much of the old out as is reasonably possible.