Hilton Garden Inn's Brand Standards (603.06.A - "Relocation Requirements - Guaranteed Reservations") require:
If the hotel cannot honor any confirmed or guaranteed reservation, the hotel must make a special effort to find suitable accommodations at another Brand hotel. However, if there are no Brand hotel accommodations in the area suitable to the guest, the employee must offer to find other suitable accommodations within the Hilton Portfolio of Brands. If there are no other hotels available, suitable accommodations for the guest should be secured.
and goes on to detail that the hotel must pay for first nights room and tax, transportation, and any other "necessary expense incurred by the change"
And 701.03.D ("Member Relocation and Recovery"), while parroting substantially all of the language in 603.06 also includes
2. The hotel must complete the “Reservations Emergency Stay Credit” form online via The Source to provide the member proper Points & Miles, stay credit, and applicable bonuses for the eligible stay they would have consumed.
If you were a Diamond member 701.02.D.4 raises some interesting additional benefits (including a cash "inconvenience" payout), but given the nature of the situation it would hardly seem sporting to try to claim them (and it's not clear if OP is a Diamond)