I don't know what your seedling is. Regarding your old peat moss, any new seeds that you have sown that may have been treated with sprouting hormones could have enabled old seed to sprout this year. So whatever you had in it last year that didn't sprout could be what you are seeing now. It's not an exceedingly uncommon occurrence in my experience. As a matter of fact, you can sometimes get old seed packets to improve their germination rate by mixing them with other treated seed. And another facet to this is the enzymes produced from sprouting some vigorous seed might encourage older seed to sprout, too. Serendipity: it's a good thing.
