ADVICE NEEDED ASAP- party venue fully booked after invitations sent, what can I do?

[MommyGoblin]

My child sent invitations home on the last day of school with the location, time and day of the party. The party is on the 20th. I asked my partner to call and reserve a spot at the location. Found out yesterday that he forgot, called the location today to try to reserve a space but unfortunately they’re completely booked until the 28th. I don’t have ANY parents phone numbers(I lost ALL my contacts) and now I can’t host party at the location listed on invite. What can I do? I’m completely at a loss, but I don’t want to let my child down. Especially because this will be their last bday party with friends in our hometown as we are moving out of state soon.
Does anybody have any ideas or advice on what I can possibly do to make this party happen??

I struggle to believe that you can't reach a single one of the parents. Make an account on Facebook or Instagram and you reach at least half of them and be able to pass the message on to the remainder.

Why did you send out invitations without having confirmation of the venue? I understand DH forgot but he could have called and been told it was fully booked.

If you have no way of contacting them then I would book something nearby and have someone standing outside to redirect people.

Did you not have RSVPs you could respond to?

Do you not know the contact details or address of any of his classmates? If I lost my contact details, I could put a note through the door of one of the nearby friends asking them to message me and then see if they could share contacts or pass the message on. Although without some sort of class WhatsApp group, you will still miss some people. So DP with a sandwich board it is.