were the ones your friend got you dried? like toomuchtv said, unless you have LOTS of experience identifying, there is no way to be sure. there are thousands of unidentified "little brown mushrooms" species that all kinda look the same, especially when dry.
as for what you ARE looking for, psilocybe cubensis (the most common home-grown species) can be found on cow patties or cow-fertilized grassland in warm weather after a rain. this species grows in this habitat across the globe, from thailand to texas. if you have experience with the climate and timing of this species, it can be a fairly predictable one to look for, although there are tons of "strains" that can exhibit a wide variety of morphological characteristics, depending on growing conditions and genetics.
in cooler climates you may find psilocybes of the woodlover family (cyanescens, azurescens, subaeruginosa) but they typically fruit during the cool fall months. beware, the common galerina can look almost identical to the woodloving psilocybes, and can even grow right next to them. but instead of tripping, you will die.
liberty caps (psilocybe semilanceata) are also a common temperate species, common to pasture grass.
in tropical climates you may find dung-loving panaeolus species after a rain.
with all of the above species, blue bruising may be noted, but is BY NO MEANS a positive identifier. likewise, active species may display zero blue reaction. if your friend went hunting in the wild for his booms, ask him to take you one time so he can show you the ropes. mushroom identification is part science, part art. good hunters say they can identify by smell, but for me it's mostly texture in the PNW.
EDIT: if there are hundreds growing and the spot is in a public location, then it's probably NOT active, because there are plenty of people like you looking out for these guys

the best sign that you found an active patch is the telltale evidence of inexperienced pickers who grab handfulls of soil with their harvest, destroying the patch.