Luno investment claim

Good day My son passed away last year Oct his friend came to visit me in January he asked did I claim my son's money at luno so I told him I don't know anything about that, he told me to go to luno building in Cape town, so instead of going I sent an email and I was honest told them I was informed by his friend. They asked for his ID NUMBER I sent it to them and they said they can't track the account with his ID NUMBER but then what I don't understand they asked me to send documents like a copy of death certificate, a proof of his bank account, a letter of authority from court that I've got a right to his account,a proof of residential address and something. These sound like claiming documents to me but when I asked they said is to check thoroughly for his account. My problem is, isn't the ID NUMBER the best tool they can use why these documents if he doesn't have the account with them and I've been dealing with different consultants the whole time. Please help