The contamination of a product happens from time to time as Tony mentioned. I got lucky with the ALT70 as I got the word about it the day before it was scheduled to go out..... I wasn't so lucky in 01, when we sprayed Betasan that was contaminated with Round-up - that was a fun few months....
It happens on from every side. I've seen applications burn when the weather changed unexpectantly, fertilizer burn from the spreader not being turned on or something breaking, overlaps from careless operators, someone accidently spraying Roundup as the drum looked the same as the fungicide they were supposed to spray and just grabbed it, to name but a few. (And for clarity, I'm not a walking disaster! These were just ones I'd witnessed/seen at different places over the years - like the Farmers Insurance"we know a thing or two" ads!). There are so many ways it can happen, some you get away with and others you don't.
When I first became a superintendent an older one also dropped the "you're not a superintendent until you've lost some grass and recovered". Personally I think you need to be not be afraid to lose a little turf as then you can see how far you can push things, but the goal is to avoid mistakes like misapplication of a product.
To the original post, recovery would depend on exactly what was put out. Some chemicals would have a very long residual and prevent seed to grow but most of the time it can be worked around with aeration, charcoal to neutralize it, watering to flush it etc. It takes time so patience is important, otherwise, the alternative is to rip the soil out and rebuild.