Loquo is just a platform to get the publisher and the interested party in contact. To contact the person who published the listing you must do it directly trough its personal email or phone number available as contact information. (How can I respond to a listing without contact info?)
If the poster has decided not to show his email address, you will see the following under the ad title:
€Send an email to the poster€
By clicking on it, you will be redirected to an area from where you may send an email to the poster. Simply fill in the email address and message fields and click €Send€. Your message will be automatically delivered to the poster€s inbox.