It should be right where it was.  Adding companies never deletes other companies.

Where are you looking where it seems to be gone?

Resolution for 'Adding companies issue: 'I had 3 companies on my qb and added one. now one of the others is gone. and i cant find it' available: Yes.

The Adding companies issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the Adding companies issue yourself by looking for a resolution described in the article. If it is a complex Adding companies issue or you are unable to solve the issue, you may contact us by clicking here or by using other Adding companies support options.

For more information about resolving issues related to Adding companies in Quickbooks/QBO or to get support for the issue 'I had 3 companies on my qb and added one. now one of the others is gone. and i cant find it', click the link below: