Blogger has this weird thing whereby if you try and go back to edit a post you've already published -- especially one that contains Amazon iframe code or YouTube or other video code -- it'll disappear as soon as you open it to edit it!
The way to get around this is to go to Settings link tab, click Basic and go down to where it says "Show compose mode for all your blogs?" as pictured here.
Turn that question to "No" and click "Save Settings" -- and you'll have your blog post back to edit nicely.
If you're not a coder and not used to stuff outside of the "What You See is What You Get" or WYSIWYG mode -- things might look a little tricky with all that HTML code and stuff.
But just keep clicking the "Preview" mode Blogger gives you to see if it looks okay, play around, Google for code questions and you'll be fine.