likely not be on any registry or other visitors--and perhaps even friends/family members didn't know they were headed to the Guadalupe River or areas nearby.
As I mentioned a few days ago, the number 144 is the current total lost in the Colorado Big Thompson Flood just shy of 50 years ago, yet every time the media (especially newspapers) do a retrospective with a pending memorial anniversary, they hear from someone who has long believed a lost friend or relative-long disappeared- was there and not officially among the unaccounted for. Occasionally, they are able to prove it and likewise remove someone from the official "missing" list who was later found not to be in the area. And yes, there can be those who use the episode as a chance to "officially disappear." All of this is harder today, of course, but elements will make it hard to be absolutely certain of the final tally.
Truly a horrible tragedy for those parents and all others lost. 'Impossible to know what to say beyond that. 
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