Updated
It happens all the time. A phone is lost on the last night, a LINE account does not survive the move to a new handset, or her messages simply stop arriving and her profile picture turns grey. Before you assume the worst, work out which of three things happened, because each has a different fix.
If you changed phones or reinstalled LINE, your friends list usually comes with your account, as long as the account was linked to a phone number, an email address or another sign-in you still have. Your chat history is a separate thing: it only comes back if you had a backup (to Google Drive on Android, or iCloud on iPhone). So it is possible to have her in your friends list with the whole conversation gone. Open your friends list and search her name before anything else. If she is there, write to her. She will not know the history disappeared on your side.
If your LINE account itself is gone, because the phone number was a holiday SIM that has since expired and nothing else was linked, you have a new account and she has lost you as much as you have lost her. Go to the next sections.
If she changed phone or number, her old account may be dead and a new one may exist. Messages to the old one will sit undelivered, or be delivered to an account she can no longer open. Nothing is wrong with you; she has simply moved, and she may be looking for you too.
What not to do: do not go looking for her on every social network with her full name, and do not ask strangers online to find her for you. If she has changed number on purpose, that choice is hers. If she has changed it by accident, one of the routes above reaches her without anybody feeling tracked.
If she has joined this site, you do not need her LINE at all. Every woman here has a page under her nickname, and you can reach her through it.
If she is not on the site, she has not joined, and there is no page for her anywhere here. We never make one up.
A conversation on this site belongs to your account, not to your phone. Lose your phone, get a new one, sign in, and every conversation is where you left it, with her replies, the photos and the history. You do not need a backup, a QR code or a transfer.
It also works the other way. If she changes phone or moves to a different bar, her conversations can be reconnected to her, so you do not have to find her again from scratch. Her side needs no number from you and no friend request; she just keeps reading in Thai.
That is not an argument against LINE. It is simply a second, safer thread, so that one lost phone does not end a friendship.
If you do reach her and she does not reply, give it a few days. She may be away, busy, or unsure who is writing. A second short message reminding her where you met is fine. After that, the silence is an answer, and it deserves the same respect as a reply.
Some habits that stop this happening again:
The guide to using LINE outside Thailand covers the account and backup settings step by step.
Want to write to her in your own language? Read How it works, then Start free. Her replies are always free to read.