We're experiencing an issue where activities are lost if the application is closed before the activity is saved. You will experience this issue whether or not you pause your activity before closing the app. For now, please ensure that you do not close the application unless you save your activity first.
We are investigating this issue and hope to release a fix soon. We apologize for any inconvenience.
The issue has been resolved in version 41.1.0. Once you install this version from the app store and open the Strava app your previous recording will be available on the recording screen. If you experienced this bug during multiple recordings please save the initial activity, fully close the application, then reopen the app repeat the steps above.
If you continue to have problems please proceed with submitting a support ticket.
Follow this article for email updates on the issue.