Assign anonymous node to user Id
You can use Entity Reference Prepopulate.


  Allow prepopulating any Entity reference field via URL


In your booking-request set up an entity reference field pointing to user entities. Then, create a link in the listing node to booking-request node add form with the right parameter to prepopulate that entity reference field.

See README in the module:


  In order to pre-populate an entity reference field you have to supply
  the parameter in the URL.
  
  The structure is node/add/article?[field_ref]=[id]
  
  Where [field_ref] is the name of the entity reference field and [id]
  is the id of the entity being referenced.
  
  Examples: node/add/article?field_foo=1 node/add/page?field_bar=1,2,3