It is a theft to find lost property and not return it whether its found in Carlsbad or anywhere in California. California penal Code 485 basically staes it is a theft to approrriate found property as your own under circumstances which give you knowledge of the true owner or a means of inquiry as to the true owner. It is misdemeanor petty theft if the value of the property is $950 or less and felony grand theft if $950 or more.
Burglary is different than theft. Theft is either grand theft if over $ 950 in value or petty theft if under. Grand theft is a felony but can be reduced to a misdemeanor, petty theft is always a misdemeanor unless there are prior theft offenses. Burglary is the entry in to a building with the intent to commit any theft, grand or petty, or any other felony. It is the "entry with intent" which is the crime and is always a felony but can be reduced to a misdemeanor at some point, as long as the building entered was a commercial building and not a residence. It is considered 2nd degree.