Why would my boyfriend archive and mute a WhatsApp conversation?

So I did something bad , I went into the rabbit hole and took a look at my boyfriend phone. On his archived WhatsApp message there was a chat with some girl aperently from his Uni time. There chat was cut in the middle (like the conversation was deleted ) then she texted an answer to a question that wasn’t there anymore. The conversation was definitely hidden since it was archived and muted. Should I be worried? Like why would he delete the chat then keep some of it and archive and delete it
Why would my boyfriend archive and mute a WhatsApp conversation?
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