Updating Search Results between sessions

I'm working with displaying search results on a mobile device - The search results are ever changing. On an hourly basis new results are added and unavailable results are removed. For more context, it's the rental property industry.

I'm looking at ways to update these search results between 'micro' sessions on a mobile device.

Use Case: - The user performs a search and scrolls down the list of results - the user then leaves the app for x amount of time - The user then returns to the app.

In the above use case, the time between 1st and 2nd sessions, the search results have changed.

What is the best way to make the user aware of updates to their search results?