If you still haven’t been able to recover the missing tabs on Safari, this final method should help. Every time you access a website on the internet — as long as you’re not in Private Browsing mode — Safari stores its address in your history. Even if you can’t find your tabs in the web browser, there will be a record of the websites you’ve visited, assuming you haven’t deleted it along with Safari’s cookies. If you use an iPhone or an iPad, open Safari and tap on the book icon to select ‘History’; you’ll see a chronological list of all the websites you’ve opened recently, including those you could not access.
You can also use this method on Mac: open the web browser, click on ‘History’ on the menu bar, and select ‘Show All History.’ In addition to the list of visited sites, you can search for a particular website in the search bar, and double-click to open it. If you want to make doubly-sure you won’t lose important tabs again, there’s an easy way to save them from vanishing in the first place. In Safari, tap and hold the book icon and select ‘Add Bookmarks for X Tabs,’ where X represents the number of tabs. Later, you can open the whole group of tabs from the bookmark section (via MacRumors).