[mtqwerty]

PCR will only amplify DNA that exists in a sample. If you get a partial sample, running it through PCR will just give you more of what you already have. Helpful if you need a specific concentration of DNA to run an assay but not helpful otherwise.

It is possible to link a person to a partial DNA sample with something like patterns in SNPs but PCR won't help you create a full genome from a partial one.

Not sure if OP was misspeaking when they said "not enough to sequence" but they may have meant, not enough DNA to get a definitive match with the database samples.