Restore seems like the best possible option here. We've got opposite pairs outside of “Un-” as in “UnTrash” like “collapse” + “expand”.

The up arrow idea feels a bit odd – it'd be like expand (and the opposite would feel like compress) the rubbish or something confusing. Not sure.

Compared to a striked through trash can still an improvement IMO. The use case for this icon is meant to be only actions that follow an icon signified by 'trash', not other functionalities like page restore for example…
The example from the task description on the other hand has too many details: https://www.freeiconspng.com/img/12269

Change 497018 had a related patch set uploaded (by VolkerE; owner: VolkerE):
[oojs/ui@master] icons: Cahnge and rename 'unTrash' to 'restore'

https://gerrit.wikimedia.org/r/497018

Also let's bear in mind that currently there doesn't seem to be any use of 'unTrash' right now… https://codesearch.wmflabs.org/search/?q=%27unTrash%27&i=nope&files=&repos=

@Volker_E, dropping in to +1 restore vs. un-trash

I do agree with @Jdforrester-WMF that the current icon feels a bit off, I wonder what 'opening' the trash can might look like (essentially tipping the lid slightly like in the example that you shared).

@cmadeo Thanks for the feedback, the problem is we don't have any space on the canvas left to the top. We could reduce the size of the bin, but that would imply other side-effects…?!

@Volker_E oof, yeah having it be smaller than the other trash icon would be bad :(

Change 497018 merged by jenkins-bot:
[oojs/ui@master] icons: Change and rename 'unTrash' to 'restore'

https://gerrit.wikimedia.org/r/497018

Change 541905 had a related patch set uploaded (by VolkerE; owner: VolkerE):
[mediawiki/core@master] Update OOUI to v0.35.0

https://gerrit.wikimedia.org/r/541905

Change 541905 abandoned by VolkerE:
Update OOUI to v0.35.0

Reason:
for v0.35.1, which is on its way

https://gerrit.wikimedia.org/r/541905