I lost the reputation just 10-15 minutes ago and not 5hrs ago as it shows. And moreover I remember I only edited the question long back(Do not remember the date). Now it shows the question was removed, and I surprisingly I lost rep. What are the reasons for which I lost the rep?
Actually it's not surprising considering the changes that occurred this Spring (if I remember well), you can read more here: Reputation and Historical Archives. When a question or answer is deleted, you lost the rep you gained thanks to them (or you get it back if you were downvoted).
You can keep it in some cases, from the same blog post Reputation and Historical Archives:
if you’ve contributed something worthwhile to the site, you should keep the reputation for that even if it eventually gets deleted. “Worthwhile” here is defined as,
- A score of 3 or greater
- Visible on the site for at least 60 days
Score from edits is not included here, so you lost it.
The question was indeed deleted 5 hours ago by the user that asked the question. Some corrections to reputation are not instantly applied but require a script that runs periodically. You lost the +2 reputation you got for editing the question on July 30th simply because the question isn't there anymore.