When you check your WhatsApp account, there is no way to tell if someone has deleted your number from their contact list. However, there are a few things you can look for that may give you a clue. If you see that all of your messages to this person are marked as delivered but they never appear online and you never receive a response, it's possible they have deleted your number. Another possibility is that they have simply blocked you on WhatsApp so that they cannot receive any of your messages.