Thanks for bringing this issue to our attention. I'm here to provide information about your invoices disappearing in QBO.
I've checked our system to see if we have any reports on other customer's experiencing the same thing and there was no current feedback. With you encountering this behavior, I suggest performing some basic troubleshooting steps.
There's a possibility that this can be one of QuickBooks unexpected behavior. To isolate this concern, you may use a private browser to disable browsing history and the web cache. This allows a person to browse the Web without storing local data that could be retrieved at a later date.
Before doing so, you need to save necessary information such as login IDs’ and passwords.
Please know that we value your patience while dealing with this concern. Let me know how things go after following the above steps. I'll be on the lookout for your reply and to further assisting you if you have other questions. Wishing you and your business continued success.