Enterprise admin removed from domain admin group in a child domain.

[fvh]

Who can help?
Situation: somebody removed the enterprise admin user from the domain administrator group in a child domain.
Therefore some specific enterprise admin jobs can not be performed anymore in that child domain. (creating sitelinks, authorizing dhcp servers, etc).
We do not have physical acces to the domain controllers of that child domain.
How can we reenter the enterprise admin user back in the local domain admin group so that we regain access to that child domain ?

All help welcome,

Thanks in advance.