Do we have any recorse for someone who sold house to us?

Yes. Typically sump pumps are considered permanently attached to the property and therefore stay with the property. The portable humidifier by definition is not permanent.

But understand that a sump pump is not part of the sewage system. Instead it serves as a back up system to a sump basin when basements exist below the local water table to redirect water away from the house. Often people direct their washing machine waste water to sump basins, but not their toilets, so any damage that resulted from the overflow is arguably your own fault depending on the situation. Long story short, considering the expense of lawyers and court costs you might want to skip suing your seller for damages and just go to small claims for the value of the pump. And in the mean time, put a new one in.

If the sump pump was part of the house contract, then you have grounds for theft--which you should pursue immediately. Do not delay in getting this problem taken care of. If you move in without complaint, you can be said to have "accepted" the house as is. So get a lawyer.

Unless otherwise stated in the purchase agreement, the sump pump was real property and was part of the property. The seller should never have removed it.

And since it was part of the property, it would be assumed that the pump was there. By removing it and not telling you, they are responsible for the damage.

You need to talk with a lawyer. But I would say you have a very strong case for damages from the seller.

A house typically is purchased with its "permanent fixtures" remaining, in the USA (not so much in other places). Something "permanent" generally includes things that would require tools to remove, unless otherwise specifically mentioned in the contract (e.g., "plate-glass mirrors in exercise room are not included").

The person who removed your property is a thief. Report the theft. They may claim it was "a misunderstanding", in which case you simply negotiate how much they're going to reimburse you for the replacement pump and the damage they caused.

If the sump pump was included among the personal property to be transferred you'd be entitled to it, but if the contract of sale included a clause saying any claims must be resolved at the closing you may have waived it. However, any damage occassioned by negligence you may have a claim for damages, but you'll have to sue if they don't pay your damages.

Same with the humidifier, but no negligence claim is available. If you had a lawyer, check with him/her first.

if the sump pump was part of the purchase, sue her

the portable humidifier is probably not included in the purchase