WebDriver - sendKeys(input) does not complete before sendKeys(Keys.RETURN)
Try this, once you enter the input into the search box, check whether the text is completely present or not inside the text box again using if statement, if complete text is present, then do the sendkeys(keys.return) part.
Just give it a try. Because once you entered the text into text box, in the next step the element obviously will be there.
Thank you,Shravan Kumar.T