As a quick fix, If you can identify what wire from the now non-existant 7 way plug, fed the brakes, you can hard wire (connect the brake wire from the Coach, to the brake wire on the trailer). You can even install a special plug on either the coach side or trailer side. It will be one more plug connection to be made until you can get it fixed.
Depending on how bad the "mobile tech" hosed your connection
, it may be a simple work around.