My mother has been sending letters and packages to the kids for years and nothing has ever gone missing using the post office. On a couple of occasions letters and especially postcards have floated around for a few months.

Letters and postcards do not need a signature. If the item is a package the postie will come to the house and give you a slip to collect the item at the post office. You take the slip to the post office and pay i think 50 or 60 pesos and they will give you package.

How long ago did you send them? They still might arrive