But I received confirmation email when I enter the contest
Yes, if your e-mail is confirmed, you are validly entered in the social media part of the contest.
If that e-mail address is the same as the one you use on ECF, then if you win LTN will recognize that you are on ECF, will acknowledge your win here on this
thread. If the e-mail address you used for the social media part of the contest is not the same as the one used for your ECF user account then LTN wouldn't know; you would still get the prize, just that he wouldn't know that Jennifersbody was a winner.
Example: The e-mail I use with ECF, the one connected to my ECF username, is a gmail account. If I use that gmail address for the social media entry then LTN would recognize me if I win. If I instead use a hotmail email for the social media entry, which was confirmed, I can win but LTN wouldn't know that it is markfm.