The hotel cannot find your reservation. What to say

Nine times out of ten the reservation exists and is filed under something you did not expect: a different surname, the name of whoever paid, a third party booking site's own reference rather than the hotel's, or a slightly different spelling.

So the goal at the desk is not to argue. It is to give them enough different ways to look it up that one of them works.

Have these open before you speak

On screen, not in an inbox you are still searching while somebody waits.

4 things to do

The confirmation reference, and separately the booking site's reference if you booked through one.
The exact name it was booked under, which may not be yours.
The dates, and the card used to pay.
The confirmation email itself, which is the thing that ends most disputes.

Ticks are for this visit only. Nothing here is saved anywhere.

An opening that works

Something plain does the job: hello, I have a reservation with you and you are not able to find it. Can I give you a few ways to look it up.

That sentence does two useful things. It states the problem without accusing anybody, and it moves straight to the thing that actually resolves it, which is alternative search terms. Change any of it. The point is having a first sentence at all, so the opening is not the hardest part.

Ways to ask them to search

Offer these one at a time. Front desk systems search differently from how you would expect.

The hotel's own confirmation number.
The third party booking reference, which is often a completely different format.
The surname of whoever paid, rather than whoever is staying.
The card's last four digits.
The dates alone, which often surfaces it when a name is misspelled.

If it genuinely is not there

Show the confirmation email, and ask what they can do tonight rather than what went wrong. The cause matters tomorrow. Where you sleep matters now.

If they are full, ask them to find you a room at a comparable hotel, which is standard practice when a booking cannot be honoured. Get the name of who you spoke to and a reference before you leave the desk, because whoever you deal with next will not know any of this.

Then check what else this affects

If your stay moves, anything you booked around it may need a look. A dinner reservation, a transfer to the airport, a tour with a pickup at the hotel.

This is the part that catches people the next morning rather than that night, and it is covered properly in working out what else your trip depends on.