Without going down this rabbit hole too far, in the US and countries with similar legal systems, they have to establish possession before going to the next step. Contrary to popular belief it's not the dreaded "post office pickup notice signature" that's used, but a controlled delivery. Either they'll establish surveillance to observe someone physically bringing the package into your house, or, if they can't see it from a discrete location, will have an agent knock and hand it to you. Once that's. done they've established possession and can come in to search for evidence of dealing.
Generally speaking, no agency goes through this (high cost, high risk) effort looking for an end user of almost anything. They're expecting to find a distributor.
(Also peptides are an FDA issue, so a few kits is hardly likely to concern them), and no one else is going to pursue that, except possibly for growth hormone, which is specifically criminalized by its own law).