USATF rules extremely clear -
4. (a) When bib(s) are provided, every competitor shall wear them, as indicated in these
rules, when competing.
(b) If one bib is provided, it must be worn visibly on the front. When two bibs are
provided, they must be worn on the singlet, front and back. If, pursuant to Rule
143.2, a singlet is not worn, the bibs should be worn on the shorts, front and back.
The competitors may also be required to wear start list identifying numbers visibly
on the hips and in other locations determined by the Games Committee.
(c) No athlete shall be permitted to participate in any competition without the
appropriate bib, except as indicated in these rules. Bibs are to be worn as issued
(cutting or folding numbers is not permitted). The identifying information on the
bib need not be numeric. It shall be of sufficient font type, size and contrast for clear
visibility. Not wearing an assigned bib may be grounds for disqualification under
Only logical reason to hide bib is to not be identified as a competitor and sneak up
at last minute - CLEARLY ANOTHER RULE VIOLATION
Let's see if this RD enforces the rules. Wonder if drug testing was used also.