Testing on tiddlywiki.com is a bit different, since it probably has different plugins and settings as your wiki. If tw-com also fails to find the tiddler there is a bug in the core.
If it only fails with your wiki, it may be a additional core plugins, or 3rd party plugins that could cause the problem.
So testing with tw-com will help to find the problem. If you import tiddlers into tw-com, they will not be saved. Nothing leaves your device. Technically you import your tiddlers to a wiki in your browser. No data is sent to a server.