An eviction is a legal process. Your friend would have been give plenty of notice through the legal system. When the actual eviction occurs, it is handled by local law enforcement. Once the items are on the street, they will often disappear quickly. It would have been your friend's responsibilty to make arrangements for their posessions in advance.
For any legal advice, your friend would need to consult with an attorney.
It is likely that her/his things were placed on the curb, and they vanished quickly, and pretty unlikely the agent took the belongings.
Also, they need to make sure their belongings were not just put into storage for safe keeping, instead of putting them out in the elements. You may only be getting half a story from your friend.
Finally, there is a difference between an "agent" and a Realtor. If the agent is licensed, there is the Real Estate Commission that handles consumer complaints. If they are a Realtor, there is an additional option of going to the local Board of Realtors (where the Realtor is a member) and filing a complaint.