Technically it is a .357 caliber handgun, as caliber refers to barrel/bullet diameter and the barrel diameter of a Ruger LCP is .357. However, do to inconsistent naming conventions over the years, .357 caliber cartridges are frequently described as .38 caliber and it is to late to fix that.
So, moving on and accepting the above error, you are still wrong. The commonly accepted usage is that .38 caliber is the set of all handgun rounds that are either .38 in diameter, or that are named .38 or any variation thereof.
So while it would have been wrong for them to have said something like ".38 acp", or ".38 special", as those are specifically other rounds than this gun uses, .38 caliber is okay because it is a catchall term. .380 acp would have been better of course, being far more specific, but that doesn't make the article wrong. It is like the difference between describing an automobile as a "Black SUV" instead of as a "Black Toyota Highlander". Both are correct, the second is just much more specific.
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