れれっ？ 本当にないっすか？ んー、おっかしいなぁー
It's a conversation from video game, one of the characters is surprised by the answer of his companion.
My guess it's something like "Huuuh? Not really? Hmmm, strangelyyy"
It sounds like an intentionally odd or silly rendering of あれれ？, which is itself a mildly exaggerated version of あれ(っ)？, a normal expression of surprise.
Your guess about this is correct.
The rest of your guess is actually a bit less so - 本当にないっすか is 'is it really not there?', and おかしいなー is closer to 'that's strange' (it's not an adverb).
