No "amendment' since you never "activated" your H-1B status: you were readmitted to the US on L-1B status, same as before. That same employer who previously successfully petitioned you for an H-1B will now need to file a brand new petition to change your status from L-1B to H-1B. The good news is that you are cap exempt, given that you were already counted against the numerical cap back in 2013 and will remain "cap exempt" until 2019, should you decide to again "jump ship" in the interim.
Kindly be advised that the answer above is only general in nature cannot be construed as legal advice, given that not enough facts are known. It is your responsibility to retain a lawyer to analyze the facts specific to your particular situation in order to give you specific advice. Specific answers will require cognizance of all pertinent facts about your case. Any answers offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship.
Your employer with the help of their attorneys should be able to figure this one out.
This response is general in nature and cannot be construed as legal advice, given that not enough facts are known. Any comments offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship. You are encouraged to seek independent and private counseling for a complete review of your case.