Missed letters from tablet

I've installed today MS Outlook on my iPad Air 2. I received many messages from my work and after I closed my Inbox. In couple of hours, I opened my Inbox again and 3 or 5 messages disappeared. Where are it? I believe that there is a variant to see it again.

 

I don't have enough experience in searching for solutions or articles on the Internet. But I had to use some search engines like Google, Yahoo and Bing and as I found out from contacts of this resource, group of programmers created it, but I'm afraid of doing it immediately, because it is new thing for me. What opinion do you have about this masterpiece? Can I use it for my case? If someone applied it, share your thoughts how it works and how much it might be effective.

Unfortunately, I didn't find any resolutions from Microsoft - I can't realize why such huge corporation doesn't care about safety of data of their customers like me, like you. This question for me now doesn't have an answer. If someone owns this information, inform me, please.

I wasted several valuable hours of my spare time and I've no idea who or what could return me these very hours. Pats, I hope this time or next time you'll be more sympathetic to problems of strangers on your community.