I just thought of something related to the hide thing. If you think you’ve hidden something but can’t get it to show up again,and it doesn’t appear when you turn on Hidden Geometry or Hidden Objects, there are a couple of other possible reasons. One is that you assigned a tag to the object and that tag’s visibility is turned off. You should check the Tags panel for that.
The other possibility is you inadvertently hit Erase instead of Hide in the Context menu. I’ve seen others do this.
If that is what happened and the missing object is a component, it will likely still be in the In Model components. Open the Components panel, click on the house icon and you should find the component there. You can then select it and bring in a new instance to replace the deleted on. If the object is a group or ungrouped geometry it will be gone. (This is one of many reasons I prefer components to groups.)
You could probably go back to an earlier version of the model in Trimble Connect however you would lose any work you’ve done since that earlier version was created.