List Form Power Apps are stored in a default Power App envrionment
List forms Power Apps are in fact full-blown canvas apps with a few distinctive features:
- Only available in the Default environment.
- Do not require users to have a Power Apps license to work with them.
- Hidden from the UI in https://make.powerapp.com
- Can only be run from a context of SharePoint, via an iFrame.
- Can't be explicitly shared. Permissions are "inherited" from a SharePoint list.
You can list all of these hidden Power Apps via PowerShell:
Install-Module -Name Microsoft.PowerApps.Administration.PowerShell
Install-Module -Name Microsoft.PowerApps.PowerShell -AllowClobber
Add-PowerAppsAccount
Get-AdminPowerApp

While the app is hidden, you can still open it via a direct link: https://make.powerapps.com/environments/{environmentID}/apps page.
Alternatively, if you have an App ID, you can navigate to it either via a direct URL: https://create.powerapps.com/studio/#action=sp-edit-formdata&app-id={appID} or https://make.powerapps.com/environments/{environment}/apps/{appID}/details

Since this is just a canvas app, we can also see all versions of this Power Apps in the "Versions" tab.

You can export this Power App as any other canvas app:

_PowerAppsCache folder
The _PowerAppsCache folder contains cached files related to the Power App player (Aka. AppMagic.PublishedApp.Player.js
). The Power Apps player is hosted in a https://pa-content.azureedge.net site and is exposed in your SharePoint list via an iFrame.

You can delete the _PowerAppCache
folder list and your Power App form will still load with no issues.

Long story short, Power Apps are not stored in SharePoint and the _PowerAppCache folder does contain any Power Apps.