The result is not deduced by measuring the amount 3He but that of 4He. The amount of the latter is too high and since 4He produces 3He, the amount of 3He must be higher than normal if we believe in standard nuclear physics.
The first report by Fleischmann and Pons about "cold fusion" was the claim that 4He is produced by fusion of two deuterium nuclei. "Cold fusion" was labelled as pseudoscience first but now it has been accepted as a real science and cold fusion researchers are not regarded as science criminals anymore.
Could this extra 4He be produced by "cold fusion"? No extra 3He, not produced in "cold fusion", would be needed.
The TGD based model for cold fusion (see this, this, and this) relies on the notion of dark nuclei and one of the basic predictions is that heavier nuclei can be produced outside stellar cores at much lower temperatures than in the Sun. In the TGD framework, prestellar evolution would start by "cold fusion" and would lead eventually to such a high temperature that ordinary fusion would start.
"Cold fusion" solves many problems of the standard nuclear physics based view. For instance, the production of nuclei heavier and iron is poorly understood: the hypothesis that Supernovae might have produced them remains unproven. Also the abundances of many light nuclei, such as Lithium, are poorly understood. Also the model for solar fusion has an anomaly discovered a few years ago. There is also evidence that living matter produces nuclei such as Calcium by some unknown mechanism.
For a summary of earlier postings see Latest progress in TGD.