https://github.com/daltoniam/tarkit/issues/10

App Distribution Guide Debugging Deployed iOS Apps

Understanding and Analyzing Application Crash Reports

https://stackoverflow.com/questions/29119276/jetsamevent-2015-03-18-151504-ips-files-are-generated-for-crashes-instead-of
JetsamEvent log is so called Low Memory Report.
So, it is highly possible that your App was killed by system due to memory shortage.

References
-My app crashes and closes down and there is very little information as to why
-Understanding Low Memory Reports (*a little bit outdated)