According to Art. 54 EPC, a public oral description, use, exhibition, etc. is considered as prior art if the facts of the disclosure can be proved. In particular, a written document confirming the oral disclosure can even be published after the filing date of the application being searched as it is the date of the oral disclosure which is decisive under Art. 54(2).
However, the search division, in carrying out a European search, cites an oral description, etc. as prior art only if it has available a written confirmation or is otherwise convinced that the facts can be proved: the date of the non-written disclosure is given as the relevant date (see G‑VI, 3); the date of the eventual written disclosure must also be indicated.