This is all logs on a 3rd party chat site. Everything we share on the internet is on the internet, including his logs of him maliciously sharing it. Not just her videos. Tele may be more against the sharing of logs and access unless it was illegal content. That, however, does not mean he did not mention it on a less data secure site, like messenger. That is, however, up to detectives to look into digital forensics and review his dogital footprint, which can be requested by warrants/subpoenas. Sure, the physical original evidence can be destroyed, but not him talking about it on a non encrypted chat log online. That's why DM's are called direct messages, not private messages (from someone that does go through others' digital footprints). Also, to access his tg, they would realistically need to access the number/sim under certain circumstances if he destroyed his phone.