I just told you that laws are fallible.
The laws dealing with found property remain pretty much unchanged since Babylonian and biblical times, and California's penal code section dealing with found valuables is virtually identical to laws on the topic throughout the civilized world. Although some areas of the law are still fluid and subject to controversy, you'll find that the criminal laws governing the aspects of ordinary life have remained fairly well unchanged, and are well-understood and approved by the overwhelming majority of responsible people.
If you think it right for the law to require a person who finds valuable property to make a reasonable and just effort to return that property to its rightful owner then any problem you may have is not with the the law.
But the law is hardly enough by itself. It remains to determine what the facts are of a particular case, and then to apply the law to those facts. Most often in an American criminal case, this will be the job of a jury. As anyone who followed the O.J. Simpson case can tell you, sometimes California juries come to odd conclusions; nevertheless, I don't think anyone believes that the law against murder is fallible, just the occasional jury.
My experience is that when you get people together in a jury room and have them take an oath to follow the law and to be fair, a lot of the emotional non-sensical things people say to each other in chat rooms or at the water cooler stop being said fairly soon, and in the overwhelming majority of cases the jury will come to a unanimous verdict that is consistent with the judgment of most people. The judge will help--he would instruct the jury, for example, in the iPhone case, that any carelessness of the Apple employee is not a matter for the jury to consider, because it doesn't affect the duty of the finder. The judge will also instruct the jury not to consider whether Apple, Inc. is a rich or poor corporation, or whether Apple acted imprudently in entrusting a test model of new product to an engineer. In this way the legal system seeks to help make fallible people commit fewer errors.
The real discussion will then remain whether the finder acted more like someone who was looking for an excuse to keep or sell the phone, or more like someone doing everything he could, within reason, to get the phone back to its rightful owner.
California could have passed a criminal statute applying the standards of the Civil Code to this question, or it could have simply provided that unless you file a report with the authorities (police, sheriff, campus police, etc.) within so many hours of taking custody of the property, you are automatically guilty of theft. But that is not the law--the law leaves it, most often, to a group of ordinary citizens to decide, based on their own experiences and sensibilities, whether or not under all the circumstances the defendant acted reasonably and justly.
Just like the people in the jury room, we each have our own ideas, based on what we think we know at this point, about how this finder acted, and I think that is the basis for a good and interesting conversation. Based on the number of comments in this thread and the several similar ones, a lot of other people think so too.