for remedical, when they send you the letter it has a IME number that you have to give to the hospital/doctor doing the examinations. they then upload the result directly onto the e-medical system and NVDO is able to see it themselves without you even informing them.
If you were to do the remedical without that letter, then firstly you would be considered as a new applicant upfront medical and need to do a full medical examination and not just the chest x ray. They will then give you a print out which has a IME number on it that the system generated. This copy you will then have to forward to NVDO, they will need to open and go through the mail and manually update in their system with the new IME number.
Considering they called you to inform about the remedical, the chances are the the officer right away initiated a request for remedical on that day itself, why you havent received a request letter is a mystery. However, you most likely have 30 days to go do the remedical to be automatically updated in the system otherwise that IME number becomes invalid. My advice, send out an email to NDVO explaining that you got a call from them and was told that you would be sent a letter but are still waiting for it. Generally, they reply back to emails within a week from my personal experience.
