This video explains the steps and best settings for exporting your PDF from InDesign.
One reason your PDF might be mysteriously missing the bleed is that you do not have Use Document Bleed Settings checked in the PDF Export dialogue box.
An easy way to verify if your document exported correctly is to check the size in Acrobat Reader. Your finished page size ought to be .25 inches larger than your trim size. Meaning if you have ordered a 10x10 book, then your PDF page size should be 10.25x10.25. You can find this Adobe Acrobat by selecting File>Properties>Description.