I don't in any way call Telegram a secure wallet address to have for storing crypto coins, apart from mined tokens that were given out of the tapping of the phone screen.
How the telegram wallet came into full existence because of the mining of coins through telegram. Telegram owners now develop provisions for having wallets in it for easy transfer and conversion of the mined tokens, without giving much relevance to it to secure people's tokens. However, newbies then began to use it because that was what they were introduced to, to use the telegram wallet for the storage of their mined coins on the Ton network.
Lack of not having full knowledge of how to secure a crypto wallet made your friend lose his coins in his telegram wallet. Had he known how insecure a telegram wallet is, he would have learned not to release his phone to anyone to go through because of his stored crypto assets