Is every emergency landing of a commercial flight documented?
Generally there should be some kind of record of this incident but even more broadly speaking not all aviation accidents are necessarily documented or reported on a global scale. 

It depends on what country you are in and who the reporting agency is. Here in the USA the NTSB is responsible for investigations of aircraft incidents. Investigations and reports are generally the responsibility of the country in which they happen but not all countries have investigation agencies nor the means to carry out complex investigations. Historically the manufacturers as well as other nations have offered assistance when need be as the outcome is as important to them as it is to the investigating agencies. 

As for Greece their reporting agency can be found here and the list of 2006 reports here although they seem to publish the list by year that the report came out (not the year of the accident) so the 2007 list may also be of interest. Most of the reports are published in greek which I cant read and there does not seem to be one relating to Royal Jordanian. 

Not that it is a complete list by any means but wiki does not list any similar Greek aviation incidents on their compiled list. 

For the sake of completeness, what appears to be a grass field to some may actually be a grass runway (more common than you would think) and its possible what your friend described was a landing at a grass runway (field, or strip) done for a precautionary reason. A diversion like this may not cause an investigation to ensue.