That does resemble a slime mold (Myxomycota) in its plasmodium stage.
They mostly move around at night, when there is less chance of drying
out, so that's probably why you didn't see it the next day. They can
sometimes displace themselves to several metres. The same thing has
happened to me more than once, where I returned to observe a slime,
and there was no evidence anything having been there.

Unfortunately, as for the indentification, you generally need to have
a look at the fruiting body that develops after the plasmodium (slime)
differentiates into the sexual stage. The plasmdium usually consists
of a white, pink or yellow slime, and differs considerably from the
eventual sexual fruiting body that forms afterwards. Even when you
find one in the fruiting body stage, it generally requires a
microscope to correctly indentify, with the exception of several very
distinctive species.

They are altogether a beautiful and fascinating group, and one I'd
like to learn more about...For example, the blob of slime
(plasmodium) is not multicellular, it contains many nuclei in a single
mass of cytoplasm that is not seperated by membranes!! And there is
another major group called the Dictyostelida (??) that starts out as
individual cells, that are completly independant of one another, and
crawl around under logs and in damp places, but when their food supply
is diminished, they all migrate towards a common area where they
combine to form a "slime". The amazing thing, is that from this
point on, they begin to function together as an organism, rather then
as independant cells. Its kinda like if several humans, when times
get tough, could meld their bodies together to make one big human, ...

but its even more fascinating than that...

George Barron's field guide has a good selection of slime mold's in
"Mushrooms of Ontario and & Eastern Canada". I think that they are
not even considered fungi anymore, but are put in their own Kingdom,
Mycetozoa...




(I wanted to attach some photos of Slime Mold I had but my
imagehosting "host" seems to have disappered from the web.)