People should read their Travel Insurance Policy, they all seem to have different rules. Ours says you have to ring the Insurance Company within 24 hours if you are going to make a claim, give them all the details and they will give you a claim number. If it's medical treatment you have to get a full receipt from the Doctor/Dentist.
If it's lost property etc., you have to go to the Police Station with your passport and get a fully signed form from the Police with all the details of the loss or theft and get a copy of the report with a Police number. Failure to do any of this invalidates any claim.
We have claimed twice once for emergency dental treatment and once for a lost watch, both times where successful and we where paid, but we did follow all the Insurance Company rules.