Can a substance donate a proton without the proton getting accepted by another substance?
The closest thing I can find to this involves a most unlikely proton donor.  Given an appropriate base, sodium hydride donates a proton for encapsulation in the base (rather than forming a localised covalent bond), leaving the valence electrons on sodium (!) in inverse sodium hydride.  The proton is not free (a completely free proton is possible only in plasma), but analogous to complexed metal ion or solvated electron.