I went 4800 yards freestyle at 4000 feet (New Mexico State Natatorium). I'm 54 and have done past one hour swims backstroke (which is OK with me since I like to swim backstroke).
Unfortunately, for this swim, I did not include my split sheet in my entry - only the certification sheet with the final yards and timer signature. I was informed that my swim will not count because of the missing split sheet. I mailed the form, but threw away the split sheet.
The rules are clear - you have to include the split sheet. I made an honest mistake, but the organizers would not take my word. They have to follow the rules. Personally, I don't know what they do with the split sheet - perhaps to check that the splits track with the results? Only the total distance is reported in the final results.
I suppose that someone could cheat and record more yards or a faster time, but if the sport gets to that extreme, I'm going to find some other sport.
Word to the wise: do the paperwork!