In addition to the comments of the answer from Tory, because a comment does not allow the amount of test :-(

This is the information from the help system:

Deleting test artifacts

When you delete an artifact, it is moved to the Trash view, but it is not permanently deleted from the database. From the Trash view, you can permanently delete the artifacts from the database.

Attention: Artifacts that are permanently deleted cannot be recovered. In addition, in most cases you cannot recover artifacts that are moved to the Trash view, even if you do not permanently delete them. Before you delete an artifact, make sure that you understand the consequences of moving artifacts to the Trash view. For more information, see Table 1.

http://pic.dhe.ibm.com/infocenter/clmhelp/v4r0m3/topic/com.ibm.rational.test.qm.doc/topics/c_deleting_artifacts.html

Hi Natalia,

The list of test plans will not show archived test plans, which explains why you do not see it in the list. If you know the ID of the testplan, you can still access it via the following URL:

https://<HOSTNAME>:<PORT>/qm/web/console/<PROJECTAREA>#action=com.ibm.rqm.planning.home.actionDispatcher&subAction=viewTestCase&id=<ID>

It will display the test plan, saying it has been Deleted. In RQM 4.0.2 and earlier, you cannot truly delete anything (everything is merely archived). Unfortunately, once it has been archived we currently have no way to unarchive it. This is something we are actively working on implementing and it is one of the top enhancements we are considering moving forward. In 4.0.3, we introduced a Trash view to easily view which test artifacts have been deleted.

Another way to view test plans is with our APIs. First you need to determine your project area's alias using the following URL request:

https://<hostname>:<port>/qm/service/com.ibm.rqm.integration.service.IIntegrationService/projects
Please make note of the Alias associated with your project in the list.

Now to view a list of test plans in an RSS feed, enter the following which will include all test plans (including those archived):

https://<hostname>:<port>/qm/service/com.ibm.rqm.integration.service.IIntegrationService/resources/<projectAreaAlias>/testplan?includeArchived=true&etlmode=true&modifiedSince=2013-06-26T12:10:00Z

- The 'includeArchived=true' flag will include archived testplans in the feed (otherwise archived testplans are not shown)
- The 'etlmode=true' flag makes the testplan resources in the list OSLC-style links. Clicking on the testplan name will open in a UI. This is useful for manually checking which are deleted (it will say deleted in the UI).
- The 'modifiedSince' flag will only include those testplan that were modified after the given date. Note that this is using XML date/time format (http://www.w3.org/TR/xmlschema-2/#dateTime). This can help narrow down the list if you know the time before you deleted the testplan.

You can also leave these optional arguments out. By default the page size is set to return 50 test plans. You can change this to a max of 1000 by setting the Advanced Server Configuration property Max Feed Entries/Page.

I hope this helps.
Regards,
Tory