(previews of) missing attachments should not be hidden as if they never existed

[Meteor0id]

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• I have read https://github.com/signalapp/Signal-Android/wiki/Submitting-useful-bug-reports
• This isn't a feature request or a discussion topic

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Bug description

When for whatever reason an atrachment is missing, Signal Android (and Desktop also, I have not tested iOS) hides any sign of the attachment. For example if someone has once send an image with some text, all I see now is a text message.

This confuses the cconversation history. If we discussed an image or whatever file, there is now just text and I have to guess what might have been send if anything at all.

Signal should show a placeholder, can be a blur hash or something else. That allows me to see what file type was send, and at what moment, part of which message. Even if the filetype is unknown, a placeholder should still be shown to indicate something was there.

On Desktop (not sure about Android) you sonetimes see a download button on a blhr hash and when you click on it and the image can't he found the whole tthing just disappears. Let's not do that.

Screenshots

Device info

Device: Manufacturer Model XVI
Android version: 10.0.0
Signal version: 6.13.5

Link to debug log

[greyson-signal]

Is this a situation where an attachment fails to download? Or a situation where a user deletes the attachment on a message after receiving it? If the attachment is unreadable, I'm actually much more interested in logs around the attachment failure :)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Meteor0id]

Still very relevant, Signal should not remove any messages from history ever unless a user does that on purpose.
If messages disappear the remaining message history could be misinterpreted.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Meteor0id]

A tombstone for attachments is still important to have

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been closed due to inactivity.