The OP could have avoided any issues by double- and triple-checking with mutiple TG personnel to make sure that their UA/MP FF# was correctly entered into the potentially multiple systems that might be encountered with TG and other *A carriers.

For TG, successful evidence would have been the notation "UA *G" on the boarding pass stub. With this, credit should appear within 48 hours.

I've got no problem with the requirement to send in originals, (I've had to do that with LH for years), as long as they understand that subsequent communications will involve copies.