I understand your situation. The key will be whether or not the IRS considers you a "responsible party" or just a nominee.
The IRS defines the “responsible party” as the person who controls, manages, or directs the entity and the disposition of its funds and assets. There may be more than one responsible party.
Further, the “responsible party” is defined as follows:
For entities with shares or interests traded on a public exchange, or which are registered with the Securities and Exchange Commission, “responsible party” is (a) the principal officer, if the business is a corporation, (b) a general partner, if a partnership, (c) the owner of an entity that is disregarded as separate from its owner (disregarded entities owned by a corporation enter the corporation’s name and EIN), or (d) a grantor, owner, or trustor if a trust.
For all other entities, “responsible party” is the person who has a level of control over, or entitlement to, the funds or assets in the entity that, as a practical matter, enables the individual, directly or indirectly, to control, manage or direct the entity and the disposition of its funds and assets. The ability to fund the entity or the entitlement to the property of the entity alone, however, without any corresponding authority to control, manage, or direct the entity (such as in the case of a minor child beneficiary), does not cause the individual to be a responsible party.
A “nominee” is someone who is given limited authority to act on behalf of an entity, usually for a limited period of time, and usually during the formation of the entity. The “principal officer, general partner,” etc., as defined by the IRS, is the true “responsible party” for the entity, instead of a nominee. The “responsible party” is the individual or entity that controls, manages, or directs the entity and the disposition of the entity’s funds and assets, unlike a nominee, who is given little or no authority over the entity’s assets.
If you were a volunteer, and had little control over the entity, I believe you could be considered a nominee, and not a responsible party. Likewise, as the wife was given authority for a limited period of time while the company's president was in rehab.
So, while initially the IRS might look to you and the wife for the reporting, I believe you could be released from any issues by proving the facts as you have laid them out here. This would show that you were not the responsible party.
As an officer of the corporation, you can call the IRS and find out if the corporation has filed its tax return. You would need the Federal Employer ID number (FEIN), but as treasurer, I am sure you have this. The number for general customer service is 1-800-829-1040.
I hope this answers your questions! If you have any more, please feel free to ask!