Were my Notifications somehow got deleted?

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When I came back to mylot several months back, I had forgotten actually how to handle the notifications. I didn't remember the X on the right that could delete the notification once responded to. So, I went scrolling up and down, getting cross-eyed, till one friend told me to delete right after answering. Anyway, I knew that I had many notifications way back, but when I logged in, I discovered my Notifications empty. Just now, I scrolled down to find a post about my Bucket List and discovered that I had not read two responses. I think these two were some of the notifications that got lost. Does mylot delete notifications after a few days? If that is the case, I may have a lot of unanswered responses.