Short answer. Yes. Rule 96 requires like proceedings for securing an inventory and appraisement within three months of discovery whenever property not included in an earlier inventory is discovered, succeeded to, or acquired by the ward — this text still governs guardianship of incompetents like your aunt, since A.M. No. 03-02-05-SC (2003) only replaced it for minor wards.
What the law says
whenever any property of the ward not included in an inventory already rendered is discovered, or succeeded to, or acquired by the ward, like proceedings shall be had for securing an inventory and appraisement thereof within three months after such discovery, succession, or acquisition.
Rule 96, Section 7 — Inventories and accounts of guardians, and appraisement of estates. Read the full provision →
The first inventory, filed within three months
Rule 96, Section 7 requires this from the outset: a guardian must render to the court an inventory of the estate of his ward within three months after his appointment, and annually after such appointment an inventory and account, the rendition of any of which may be compelled upon the application of an interested person. That first inventory, and each annual one after it, is the baseline record the rule builds on.
Newly discovered property gets the same treatment
The rule answers your question directly: whenever any property of the ward not included in an inventory already rendered is discovered, or succeeded to, or acquired by the ward, like proceedings shall be had for securing an inventory and appraisement thereof within three months after such discovery, succession, or acquisition. Property surfacing after the first inventory was already filed is not left out of the record — the same inventory-and-appraisal process applies, with its own three-month clock starting from when it was discovered.
Sworn statements and appraisement
The rule also requires that such inventories and accounts shall be sworn to by the guardian, and that all the estate of the ward described in the first inventory shall be appraised, with the court able to call on inheritance tax appraisers for assistance. The same sworn, appraised standard applies to the later inventory covering newly discovered property.
Why this text still governs your aunt's guardianship
This provision was partly superseded for minors: A.M. No. 03-02-05-SC, the 2003 Rule on Guardianship of Minors, took over that area. But that same 2003 Rule provides that guardianship of incompetents who are not minors continues to be governed by the Rules of Court — which is exactly your aunt's situation. So the text quoted above remains the current rule for her guardian's obligation to report the newly discovered property, and the guardian cannot treat the first inventory as the end of his reporting duty.