Did you have any contract showing the terms of your investment? How many other investors were there? Was this actually a loan or a true investment?
A business litigation attorney in Orange County should be able to assist you.
There are some contractual claims for which you might be able to obtain a prejudgment writ of attachment to lien real property and personal property on the business. Other situations permit you to obtain a temporary protective order on certain assets. Otherwise, you will have to ultimately prevail on a "limited jurisdiction" state court lawsuit (which could take up to 12 months) and then enforce your judgment.
I assume that there is no written contract with a clause that says if a suit is filed the loser pays attorney's fees and collection costs. Your attorney's fees, if that is so, could exceed $20,000. Consider writing a demand letter that says if payment is not made in e.g. 30 days, you will pursue legal remedies. Hope for payment or an offer of a compromise. If no resolution, then consider cutting your claim to the Small Claims Courts max, $7,500. (The letter can then be submitted to the court. Often, such a letter generates good will with the court and makes you seem very reasonable. Bear this in mind as you draft the letter. Don't say anything jerky in the letter.)
On the other hand, if there is no wiggle room for the debtor and it is very clear that the debt is owed, and there are assets that could be seized, consider hiring a business litigator in Orange County and asking him/her to get a pre-judgment writ of attachment. A good debt collection lawyer knows how to do that. The sheriff can then execute on the writ, you can get liens against property, etc. Often, beginning to seize bank accounts and things like that can bring a debtor to the bargaining table pronto; however,if it is not crystal clear that the debt is owed and that there is no valid defense, be careful. You could be denied and then might have little alternative but to pursue the lawsuit to its bitter end. Also, be aware that courts generally require that a creditor file a surety bond before any property can be glommed on to (a legal term lol) and the cost of a bond will depend on your credit worthiness. Good luck!
You did not mention why you are entitiled to the return of your investment. How did the other party breach the agreement? Twenty thousand dollars is a substantial amount and perhaps you may be entitled to more.
There are certain pre-trial and post-judgment remedies that may be available to assist you in obtaining the amount due. You will, however, have to file a case before these are available to you. You should start by providing a written demand to the other party. The demand letter would carry more weight if it were drafted and sent by an attorney.
I wouldn't necessarily recommend that you cut your loses and sue in small claims court. I may be willing to structure my fees so that it is financially sound to have me represent you.
I am more than willing to offer you a free initial consultation. Please call me at 612-701-7767. I practice law in California (City of Orange) and Minnesota.