Lost my pen

i am kind of sad about today, i lost my expensive pen at school. i do know when it happened, in science this morning, we did a pract where we extracted DNA from a strawberry, it was definetly in the pen pocket of my lab coat then. i did indeed check the lab coat i wore after recess when i realised my pen was missing and it was not there, i also emailed the teacher who is in that lab most often if it showed up for them to tell me. after we had packed up the pract i worked on an information report for a little bit, i do not have any memory of my pen from the time of the practical and my note taking i did during that and after recess when i realised it wasnt in my pencil case, i did check my book. i am just really annoyed, that pen is $40 aud plus shipping from canada