I don't remember which bidbot it was. I just remember it happening to me last week.
Minnowbooster is slightly different. I think, and I may be wrong, but you're not bidding, you're just straight buying them from people selling votes. I think its a more or less fixed return. From experience the return is about equal or a little more to what you send them split between SBD and SP. I've only ever sent them .5 SBD few tiimes. Smartsteem is the same but they also have a bidbot.