yes reporting sick is a right all servicemen are entitled
to.
but in EXCEPTIONAL cases, and usually with the consensus of the
commander in concern, it may be decided that the serviceman would
only be allowed to report sick in camp (dont think even that is
revoked, since reporting sick in camp is rather controlled
already). this is unusual and happens only when a serviceman has
been found to be persistently taking advantage of reporting sick
outside, e.g. doc-hop, taking short mcs outside continually so that
he does not need to return to endorse his mc, etc, especially for
NSFs who has unlimited medical leave.
in your case, there may be unusual circumstances too. rather than
have us speculate here and think the serviceman may be
short-changed, why not find out the exact details and let us know
here?