FireEngine:
Report it anyway - most on and off-ramps are covered by CCTV, they should be able to find it if you have an accurate date/time.
Damn, I should have thought of that after one hair raising incident at Tristram Ave southbound on ramp. Much like the poster with his incident on the onramp. But no damage to my car, but sure nearly squeezed out an involuntary nugget.