Is there a way to undelete a deleted node (POI) ?

Having just spent a few hours trying to figure out this issue (and finding these answers among the good finds) I'd like to add that using the JOSM Undelete plugin solved my problem and I'd warmly recommend it to anyone using JOSM.

Once you know which node (or road or relation, for that matter) you want to undelete the plugin works like a charm (so long as you don't have any conflicts; missing nodes, or alike). No need to go through the trouble of downloading the XML separately (which didn't even work for me for some reason!).

In the future I'll be using this over the Potlatch (1.4) also for undeleting roads as it's more integrated to my usual work flow.

First you have to find the node. If it was a way you could use the undelete function in Potlatch. To find the node you could use a slow updating rendering like the 'no names' layer to find where the node was. Then you could use OWL to find all changes in that area. You can see that node number 343549777 was deleted 6 months ago.

For more active regions where there has been over 100 edits since the change you can use the history tab on the main page, this can be hard to look through and you might not be able to find the node in a reasonable timeframe.

Now that you have the information you could go for the lazy way and add another node with the same tags and location as the old one, or you could try to find a way to undelete the node. Just note that the node was part of the Panama relation when it was deleted (as seen on the changeset).

After finding the node ID, you can view its history. eg for that Panama City node: history

At the bottom of that page, there is a link for for "Download XML". Click on that, and save this as a .osm file. Then open this .osm file in JOSM, then upload it. This will undelete the node, keeping the same node ID and history, and restoring all of its tags.