Thankfully, Pearson HQ in the US was very helpful. Initially they still disallowed my admission because of the absence of the passport. However, they did make a concerted effort to understand my situation. And after a very length conversation and explanation to the validity of the documents that I could present to them, they told me that it was acceptable.
The basis was that I could present 4 different official documents to validate my identity.
When I turned up at Pearson in Singapore, after having gotten my document of identity, they still had received no news from Pearson in the US, but allowed me to take the test on the basis that if Pearson US did not actually allow the documents, my scores would be cancelled.
In fact, I turned up with 5 different documents
1. Document of Identity Isssued in Lieu of the passport - issued by Immigration and Checkpoints Authority, Singapore
2. Statutory Declaration of Loss of Passport - made to Commissioner of Oaths, Singapore
3. National Registration Identity Card - issued by Singapore Government
4. Singapore National Driver's Licence
5. Singapore Armed Forces Identity Card.
I came to them with everything short of a DNA sample. But even if i did, i think they wouldn't have let me in.
Good thing is I got to take the test, but under feeling really tense and tired. But pretty glad its over.