Short answer. No. Article 1435 says that if a person in representation of another sells or alienates a thing, he cannot subsequently set up his own title as against the buyer or grantee. Having sold as someone else's representative, you are estopped from later turning around and claiming the property was yours all along.
What the law says
If a person in representation of another sells or alienates a thing, the former cannot subsequently set up his own title as against the buyer or grantee.
Civil Code, Article 1435 — Agent's Estoppel. Read the full provision →
The rule: you cannot set up your own title
Article 1435 states a form of estoppel aimed squarely at your situation: If a person in representation of another sells or alienates a thing, the former cannot subsequently set up his own title as against the buyer or grantee. When you sell as another's representative, you tell the buyer, in effect, that the thing belongs to your principal and that you are merely acting for him. The law holds you to that position. You are not allowed to sell in someone else's name, take the buyer's money, and then reappear claiming you owned the property yourself and the buyer got nothing. Your earlier conduct closes that door.
Why estoppel applies
The principle is one of fair dealing and consistency. A buyer who deals with a representative relies on the representation that the principal is the owner; he shapes his decision to buy, and what he pays, around it. To let the representative later assert a secret personal title would betray that reliance and let him profit from his own contradiction. Estoppel prevents a person from denying what his own words or acts have led another to believe and act upon. Having presented yourself as acting for the owner, you cannot now deny that state of things to the very buyer who trusted it.
What this means for the buyer and for you
For the buyer, the article is a shield. He can hold you to the sale you made in the principal's name and defeat any belated claim of ownership you try to raise against him. For you, it means the moment you chose to sell as a representative, you gave up the ability to assert a personal title against that buyer over the same thing. If you truly owned the property, the time to say so was before or at the sale — not after pocketing the proceeds. The estoppel bars the inconsistent claim and protects the buyer's acquired position.
The limits of the rule
This estoppel operates between you and the buyer or grantee; it settles that you cannot use your own title to unseat him. It does not, by itself, resolve every dispute about who really owns the thing as against other people, nor does it validate a sale that fails for some independent reason. It also presupposes that you did sell in representation of another — if you sold plainly in your own name, a different analysis applies. What the article firmly forecloses is the specific manoeuvre in your question: selling as another's agent, then claiming the property was yours to defeat the buyer.