I've taken possession of an untold number of valuables while investigating auto accidents. Purses, guns, cell phones, wallets, jewelry, brief cases, laptops, etc. It's nothing new really.
If the victim is conscious but unable to keep the belongings with them we take possession of it like we would evidence, fill out a property form, and have them sign it over to me for safe keeping. If they are not able to sign I still fill out a property form and have an EMT, firefighter supervisor, or another officer sign off on the property form as a witness.
We either give it back to the victim or a confirmed family member as soon as somebody is able to receive it, usually before that shift is over, or it goes in the evidence locker at the S.O. for safe keeping.