Actually had a co-worker do just this the other day. Pt had been involved in an MVA and had bumped their head and couldn't remember own name, however was desperate to make sure their spouse knew what had happened and that we were transporting them to the hospital. Unfortunately, when they handed my co-worker their cell phone, they also said, "I can't remember that name either." My co-worker searched for the ICE listing and (thankfully this pt had programmed that into their phone) was able to notify their spouse.
The only time I have had any dealing with ICE, but in that case, it worked great.