NorthByNorthwest

Unless things have changed, your A-number is printed on your visa sticker, that won't help with the missing NOA2 though. One would think a photocopy of the visa itself would be sufficient since the visa would not have been issued without an approved petition, but since there are multiple branches of government involved that might be too much of an assumption... If it were me and the 90-day limit was approaching I'd consider filing without the NOA2, but then there's certainly a risk that the I-485 would be returned outright, or be delayed for an RFE later, so definitely a sticky situation.

See this page for info on how to submit documents through CEAC or by postal mail: https://jp.usembassy.gov/visas/immigrant-visas/family-immigration/case-status/

To add to this, some countries have totalization agreements with the US so if you don't have enough work credits in the US you may be able to count work in those other countries as well into the US system. In my case I worked for over 10 years in Japan so I qualify for basic Japanese benefits - if I for some reason were to not reach 40 quarters in the US I could transfer the Japanese credits (and lose Japanese benefits in the process). By retirement time I'll have to look into whether it is more beneficial to keep the Japanese benefit as-is or transfer to the US. More info here: https://www.ssa.gov/international/agreement_descriptions.html#monthly I don't know if any of this applies to Medicare benefits though...