A rough topped fungi, possibly in its dying off phase. sSeen a few locally over the years, and I think I remember there being gills underneath & a short stem, but I can't be sure, and don't like to disturb/destroy 1-offs to find out :-).
This fluffy top looks to belong to Lentinus fasciatus, but we do require an image of the pores or under-surface to be certain. Try to remember that this is only the reproductive stage of the fungi, the mycelium continues to thrive within the substrate.
Point taken about the transient nature of fungi being just true for the 'visible bits'. It also reminds me to keep an eye on the same location for future appearances.