I'd rather use the past simple or present perfect, but for sure not past perfect.
If the event is finished and no present impact. For example, if you lost your keys today in the morning, then your friend came with another key and you entered your flat, and at night you are telling your brother this story. In this case you may say "I lost my key today in the morning".
If the event took place in the past, yet it has its influence or impact in the present, take the above example again. If you lost your keys, yet you can't enter you flat, then your brother called you. In this case you may tell him "I've lost my keys, and I can't open the door".
I guess it doesn't work here at all. Past perfect is used to describe an event before one or more events took place in the past. Example, We had had our dinner, then my neighbour came to watch the daily TV show with us.
Hope this is useful and for more clarification, I recommend you to see these lessons on how to use tenses by Anglo-Link on the YouTube: