Legal Question in Business Law in California

Yes. You also can have a case for purchase money resulting trust, and a number of other claims. Conversion is actually one of the weaker claims you could assert in such a situation.

Probably, but it depends upon the nature of the transfer. I would need more information before I could offer any guidance.

You probably have multiple causes of action. A lot depends on the intent of the parties and any agreements reached (oral or written) and history between you and the person holding the funds.

You have various possible causes of action and claims. Make them all and hope to prove them. If serious about hiring counsel to help you in this, and if this is in SoCal courts, feel free to contact me.

A purchase-money resulting trust would arise if the person actually bought property in his name using your money.

See my answer to your follow-up question for some conceptual categories of law that might apply to your case, under varying sets of facts.