Hi there @Niting - sorry to hear about your missing files.
When is the last time you remember seeing them on the website and how did you upload them in the first place?
Could you have a look at your events page and let me know what you find?
This is the place where all uploads, edits, and deletions are normally logged, so it should give you a hint.
Keep me posted on your findings and we'll take it from there.